action concur with proofs of recent elevation, besides those coloured
red from being fringed by coral-reefs. Thus I hope to show in a future
volume, that nearly the whole line of the west coast of South America,
which forms the greatest volcanic chain in the world, from near the
equator for a space of between 2,000 and 3,000 miles southward, has
undergone an upward movement during a late geological period. The
islands on the north-western shores of the Pacific, which form the
second greatest volcanic chain, are very imperfectly known; but Luzon,
in the Philippines, and the Loo Choo Islands, have been recently
elevated; and at Kamtschatka[36] there are extensive tertiary beds of
modern date. Evidence of the same nature, but not very satisfactory,
may be detected in Northern New Zealand where there are two volcanoes.
The co-existence in other parts of the world of active volcanoes, with
upraised beds of a modern tertiary origin, will occur to every
geologist.[37] Nevertheless, until it could be shown that volcanoes
were inactive, or did not exist in subsiding areas, the conclusion that
their distribution depended on the nature of the subterranean movements
in progress, would have been hazardous. But now, viewing the appended
map, it may, I think, be considered as almost established, that
volcanoes are often (not necessarily always) present in those areas
where the subterranean motive power has lately forced, or is now
forcing outwards, the crust of the earth, but that they are invariably
absent in those, where the surface has lately subsided or is still
subsiding.[38]
[36] At Sedanka, in latitude 58° N. (Von Buch’s “Descrip. des Isles
Canaries,” page 455). In a forthcoming part, I shall give the evidence
referred to with respect to the elevation of New Zealand.
[37] During the subterranean disturbances which took place in Chile,
in 1835, I have shown (“Geolog. Trans.” 2nd Ser., vol. v., page 606)
that at the same moment that a large district was upraised, volcanic
matter burst forth at widely separated points, through both new and
old vents.
[38] We may infer from this rule, that in any old deposit, which
contains interstratified beds of erupted matter, there was at the
period, and in the area of its formation, a _tendency_ to an upward
movement in the earth’s surface, and certainly no movement of
subsidence.
_On the relations of the areas of Subsidence and Elevation_.—The
immense surfaces on the map, which, both by our theory and by the plain
evidence of upraised marine remains, have undergone a change of level
either downwards or upwards during a late period, is a most remarkable
fact. The existence of continents shows that the areas have been
immense which at some period have been upraised; in South America we
may feel sure, and on the north-western shores of the Indian Ocean we
may suspect, that this rising is either now actually in progress, or
has taken place quite recently. By our theory, we may conclude that the
areas are likewise immense which have lately subsided, or, judging from
the earthquakes occasionally felt and from other appearances, are now
subsiding. The smallness of the scale of our map should not be
overlooked: each of the squares on it contains (not allowing for the
curvature of the earth) 810,000 square miles. Look at the space of
ocean from near the southern end of the Low Archipelago to the northern
end of the Marshall Archipelago, a length of 4,500 miles, in which, as
far as is known, every island, except Aurora which lies just without
the Low Archipelago, is atoll-formed. The eastern and western
boundaries of our map are continents, and they are rising areas: the
central spaces of the great Indian and Pacific Oceans, are mostly
subsiding; between them, north of Australia, lies the most broken land
on the globe, and there the rising parts are surrounded and penetrated
by areas of subsidence,[39] so that the prevailing movements now in
progress, seem to accord with the actual states of surface of the great
divisions of the world.
[39] I suspect that the Arru and Timor-laut Islands present an
included small area of subsidence, like that of the China Sea, but I
have not ventured to colour them from my imperfect information, as
given in the Appendix.
The blue spaces on the map are nearly all elongated; but it does not
necessarily follow from this (a caution, for which I am indebted to Mr.
Lyell), that the areas of subsidence were likewise elongated; for the
subsidence of a long, narrow space of the bed of the ocean, including
in it a transverse chain of mountains, surmounted by atolls, would only
be marked on the map by a transverse blue band. But where a chain of
atolls and barrier-reefs lies in an elongated area, between spaces
coloured red, which therefore have remained stationary or have been
upraised, this must have resulted either from the area of subsidence
having originally been elongated (owing to some tendency in the earth’s
crust thus to subside), or from the subsiding area having originally
been of an irregular figure, or as broad as long, and having since been
narrowed by the elevation of neighbouring districts. Thus the areas,
which subsided during the formation of the great north and south lines
of atolls in the Indian Ocean,—of the east and west line of the
Caroline atolls,—and of the north-west and south-east line of the
barrier-reefs of New Caledonia and Louisiade, must have originally been
elongated, or if not so, they must have since been made elongated by
elevations, which we know to belong to a recent period.
I infer from Mr. Hopkins’ researches,[40] that for the formation of a
long chain of mountains, with few lateral spurs, an area elongated in
the same direction with the chain, must have been subjected to an
elevatory movement. Mountain-chains, however, when already formed,
although running in very different directions, it seems,[41] may be
raised together by a widely-acting force: so, perhaps, mountain-chains
may subside together. Hence, we cannot tell, whether the Caroline and
Marshall Archipelagoes, two groups of atolls running in different
directions and meeting each other, have been formed by the subsidence
of two areas, or of one large area, including two distinct lines of
mountains. We have, however, in the southern prolongation of the
Mariana Islands, probable evidence of a line of recent elevation having
intersected one of recent subsidence. A view of the map will show that,
generally, there is a tendency to alternation in the parallel areas
undergoing opposite kinds of movement; as if the sinking of one area
balanced the rising of another.
[40] “Researches in Physical Geology,” Transact. Cambridge Phil. Soc.,
volume vi, part i.
[41] For instance in S. America from latitude 34°, for very many
degrees southward there are upraised beds containing recent species of
shells, on both the Atlantic and Pacific side of the continent, and
from the gradual ascent of the land, although with very unequal
slopes, on both sides towards the Cordillera, I think it can hardly be
doubted that the entire width has been upraised in mass within the
recent period. In this case the two W.N.W. and E.S.E. mountain-lines,
namely the Sierra Ventana and the S. Tapalguen, and the great north
and south line of the Cordillera have been together raised. In the
West Indies the N. and S. line of the Eastern Antilles, and the E. and
W. line of Jamaica, appear both to have been upraised within the
latest geological period.
The existence in many parts of the world of high table-land, proves
that large surfaces have been upraised in mass to considerable heights
above the level of the ocean; although the highest points in almost
every country consist of upturned strata, or erupted matter: and from
the immense spaces scattered with atolls, which indicate that land
originally existed there, although not one pinnacle now remains above
the level of the sea, we may conclude that wide areas have subsided to
an amount, sufficient to bury not only any formerly existing
table-land, but even the heights formed by fractured strata, and
erupted matter. The effects produced on the land by the later elevatory
movements, namely, successively rising cliffs, lines of erosion, and
beds of literal shells and pebbles, all requiring time for their
production, prove that these movements have been very slow; we can,
however, infer this with safety, only with respect to the few last
hundred feet of rise. But with reference to the whole vast amount of
subsidence, necessary to have produced the many atolls widely scattered
over immense spaces, it has already been shown (and it is, perhaps, the
most interesting conclusion in this volume), that the movements must
either have been uniform and exceedingly slow, or have been effected by
small steps, separated from each other by long intervals of time,
during which the reef-constructing polypifers were able to bring up
their solid frameworks to the surface. We have little means of judging
whether many considerable oscillations of level have generally occurred
during the elevation of large tracts; but we know, from clear
geological evidence, that this has frequently taken place; and we have
seen on our map, that some of the same islands have both subsided and
been upraised. I conclude, however, that most of the large blue spaces,
have subsided without many and great elevatory oscillations, because
only a few upraised atolls have been observed: the supposition that
such elevations have taken place, but that the upraised parts have been
worn down by the surf, and thus have escaped observation, is overruled
by the very considerable depth of the lagoons of all the larger atolls;
for this could not have been the case, if they had suffered repeated
elevations and abrasion. From the comparative observations made in
these latter pages, we may finally conclude, that the subterranean
changes which have caused some large areas to rise, and others to
subside, have acted in a very similar manner.
_Recapitulation_.—In the three first chapters, the principal kinds of
coral-reefs were described in detail, and they were found to differ
little, as far as relates to the actual surface of the reef. An atoll
differs from an encircling barrier-reef only in the absence of land
within its central expanse; and a barrier-reef differs from a
fringing-reef, in being placed at a much greater distance from the land
with reference to the probable inclination of its submarine foundation,
and in the presence of a deep-water lagoon-like space or moat within
the reef. In the fourth chapter the growing powers of the
reef-constructing polypifers were discussed; and it was shown, that
they cannot flourish beneath a very limited depth. In accordance with
this limit, there is no difficulty respecting the foundations on which
fringing-reefs are based; whereas, with barrier-reefs and atolls, there
is a great apparent difficulty on this head; in barrier-reefs from the
improbability of the rock of the coast or of banks of sediment
extending, in every instance, so far seaward within the required
depth;—and in atolls, from the immensity of the spaces over which they
are interspersed, and the apparent necessity for believing that they
are all supported on mountain-summits, which although rising very near
to the surface-level of the sea, in no one instance emerge above it. To
escape this latter most improbable admission, which implies the
existence of submarine chains of mountains of almost the same height,
extending over areas of many thousand square miles, there is but one
alternative; namely, the prolonged subsidence of the foundations, on
which the atolls were primarily based, together with the upward growth
of the reef-constructing corals. On this view every difficulty
vanishes; fringing reefs are thus converted into barrier-reefs; and
barrier-reefs, when encircling islands, are thus converted into atolls,
the instant the last pinnacle of land sinks beneath the surface of the
ocean.
Thus the ordinary forms and certain peculiarities in the structure of
atolls and barrier-reefs can be explained;—namely, the wall-like
structure on their inner sides, the basin or ring-like shape both of
the marginal and central reefs in the Maldiva atolls—the union of some
atolls as if by a ribbon—the apparent disseverment of others—and the
occurrence, in atolls as well as in barrier-reefs, of portions of reef,
and of the whole of some reefs, in a dead and submerged state, but
retaining the outline of living reefs. Thus can be explained the
existence of breaches through barrier-reefs in front of valleys, though
separated from them by a wide space of deep water; thus, also, the
ordinary outline of groups of atolls and the relative forms of the
separate atolls one to another; thus can be explained the proximity of
the two kinds of reefs formed during subsidence, and their separation
from the spaces where fringing-reefs abound. On searching for other
evidence of the movements supposed by our theory, we find marks of
change in atolls and in barrier-reefs, and of subterranean disturbances
under them; but from the nature of things, it is scarcely possible to
detect any direct proofs of subsidence, although some appearances are
strongly in favour of it. On the fringed coasts, however, the presence
of upraised marine bodies of a recent epoch, plainly show, that these
coasts, instead of having remained stationary, which is all that can be
directly inferred from our theory, have generally been elevated.
Finally, when the two great types of structure, namely barrier-reefs
and atolls on the one hand, and fringing-reefs on the other, were laid
down in colours on our map, a magnificent and harmonious picture of the
movements, which the crust of the earth has within a late period
undergone, is presented to us. We there see vast areas rising, with
volcanic matter every now and then bursting forth through the vents or
fissures with which they are traversed. We see other wide spaces slowly
sinking without any volcanic outburst, and we may feel sure, that this
sinking must have been immense in amount as well as in area, thus to
have buried over the broad face of the ocean every one of those
mountains, above which atolls now stand like monuments, marking the
place of their former existence. Reflecting how powerful an agent with
respect to denudation, and consequently to the nature and thickness of
the deposits in accumulation, the sea must ever be, when acting for
prolonged periods on the land, during either its slow emergence or
subsidence; reflecting, also, on the final effects of these movements
in the interchange of land and ocean-water on the climate of the earth,
and on the distribution of organic beings, I may be permitted to hope,
that the conclusions derived from the study of coral-formations,
originally attempted merely to explain their peculiar forms, may be
thought worthy of the attention of geologists.
APPENDIX.
CONTAINING A DETAILED DESCRIPTION OF THE REEFS AND ISLANDS IN PLATE
III.
In the beginning of the last chapter I stated the principles on which
the map is coloured. There only remains to be said, that it is an exact
copy of one by M. C. Gressier, published by the Dépôt général de la
Marine, in 1835. The names have been altered into English, and the
longitude has been reduced to that of Greenwich. The colours were first
laid down on accurate charts, on a large scale. The data, on which the
volcanoes historically known to have been in action, have been marked
with vermillion, were given in a note to the last chapter. I will
commence my description on the eastern side of the map, and will
describe each group of islands consecutively, proceeding westward
across the Pacific and Indian Oceans, but ending with the West Indies.
The WESTERN SHORES OF AMERICA appear to be entirely without
coral-reefs; south of the equator the survey of the “Beagle”, and north
of it, the published charts show that this is the case. Even in the Bay
of _Panama_, where corals flourish, there are no true coral-reefs, as I
have been informed by Mr. Lloyd. There are no coral-reefs in the
_Galapagos_ Archipelago, as I know from personal inspection; and I
believe there are none on the _Cocos, Revilla-gigedo_, and other
neighbouring islands. _Clipperton_ rock, 10° N., 109° W., has lately
been surveyed by Captain Belcher; in form it is like the crater of a
volcano. From a drawing appended to the MS. plan in the Admiralty, it
evidently is not an atoll. The eastern parts of the Pacific present an
enormous area, without any islands, except _Easter_, and _Sala_, and
_Gomez_ Islands, which do not appear to be surrounded by reefs.
The LOW ARCHIPELAGO.—This group consists of about eighty atolls: it
will be quite superfluous to refer to descriptions of each. In
D’Urville and Lottin’s chart, one island (_Wolchonsky_) is written with
a capital letter, signifying, as explained in a former chapter, that it
is a high island; but this must be a mistake, as the original chart by
Bellinghausen shows that it is a true atoll. Captain Beechey says of
the thirty-two groups which he examined (of the greater number of which
I have seen beautiful MS. charts in the Admiralty), that twenty-nine
now contain lagoons, and he believes the other three originally did.
Bellinghausen (see an account of his Russian voyage, in the “Biblioth.
des Voyages,” 1834, page 443) says, that the seventeen islands which he
discovered resembled each other in structure, and he has given charts
on a large scale of all of them. Kotzebue has given plans of several;
Cook and Bligh mention others; a few were seen during the voyage of the
“Beagle”; and notices of other atolls are scattered through several
publications. The _Actæon_ group in this archipelago has lately been
discovered (“Geographical Journal”, volume vii., page 454); it consists
of three small and low islets, one of which has a lagoon. Another
lagoon-island has been discovered (“Naut. Mag.” 1839, page 770), in 22°
4′ S., and 136° 20′ W. Towards the S.E. part of the group, there are
some islands of different formation: _Elizabeth_ Island is described by
Beechey (page 46, 4to edition) as fringed by reefs, at the distance of
between two and three hundred yards; coloured red. _Pitcairn_ Island,
in the immediate neighbourhood, according to the same authority, has no
reefs of any kind, although numerous pieces of coral are thrown up on
the beach; the sea close to its shore is very deep (see “Zool. of
Beechey’s Voyage,” page 164); it is left uncoloured. _Gambier_ Islands
(see Plate I., Figure 8), are encircled by a barrier-reef; the greatest
depth within is thirty-eight fathoms; coloured pale blue. _Aurora_
Island, which lies N.E. of Tahiti close to the large space coloured
dark blue in the map, has been already described in a note (page 71),
on the authority of Mr. Couthouy; it is an upraised atoll, but as it
does not appear to be fringed by living reefs, it is left uncoloured.
The SOCIETY Archipelago is separated by a narrow space from the Low
Archipelago; and in their parallel direction they manifest some
relation to each other. I have already described the general character
of the reefs of these fine encircled islands. In the “Atlas of the
‘Coquille’s’ Voyage” there is a good general chart of the group, and
separate plans of some of the islands. _Tahiti_, the largest island in
the group, is almost surrounded, as seen in Cook’s chart, by a reef
from half a mile to a mile and a half from the shore, with from ten to
thirty fathoms within it. Some considerable submerged reefs lying
parallel to the shore, with a broad and deep space within, have lately
been discovered (“Naut. Mag.” 1836, page 264) on the N.E. coast of the
island, where none are laid down by Cook. At _Eimeo_ the reef “which
like a ring surrounds it, is in some places one or two miles distant
from the shore, in others united to the beach” (Ellis, “Polynesian
Researches,” volume i., page 18, 12mo edition). Cook found deep water
(twenty fathoms) in some of the harbours within the reef. Mr. Couthouy,
however, states (“Remarks,” page 45) that both at Tahiti and Eimeo, the
space between the barrier-reef and the shore, has been almost filled
up,—“a nearly continuous fringing-reef surrounding the island, and
varying from a few yards to rather more than a mile in width, the
lagoons merely forming canals between this and the sea-reef,” that is
the barrier-reef. _Tapamanoa_ is surrounded by a reef at a considerable
distance from the shore; from the island being small it is breached, as
I am informed by the Rev. W. Ellis, only by a narrow and crooked boat
channel. This is the lowest island in the group, its height probably
not exceeding 500 feet. A little way north of Tahiti, the low
coral-islets of _Teturoa_ are situated; from the description of them
given me by the Rev. J. Williams (the author of the “Narrative of
Missionary Enterprise”), I should have thought they had formed a small
atoll, and likewise from the description given by the Rev. D. Tyerman
and G. Bennett (“Journal of Voyage and Travels,” volume i., page 183),
who say that ten low coral-islets “are comprehended within one general
reef, and separated from each other by interjacent lagoons;” but as Mr.
Stutchbury (“West of England Journal,” volume i., page 54) describes it
as consisting of a mere narrow ridge, I have left it uncoloured.
_Maitea_, eastward of the group, is classed by Forster as a high
encircled island; but from the account given by the Rev. D. Tyerman and
G. Bennett (volume i., page 57) it appears to be an exceedingly abrupt
cone, rising from the sea without any reef; I have left it uncoloured.
It would be superfluous to describe the northern islands in this group,
as they may be well seen in the chart accompanying the 4to edition of
Cook’s “Voyages,” and in the “Atlas of the ‘Coquille’s’ Voyage.”
_Maurua_ is the only one of the northern islands, in which the water
within the reef is not deep, being only four and a half fathoms; but
the great width of the reef, stretching three miles and a half
southward of the land (which is represented in the drawing in the
“Atlas of the ‘Coquille’s’ Voyage” as descending abruptly to the water)
shows, on the principle explained in the beginning of the last chapter,
that it belongs to the barrier class. I may here mention, from
information communicated to me by the Rev. W. Ellis, that on the N.E.
side of _Huaheine_ there is a bank of sand, about a quarter of a mile
wide, extending parallel to the shore, and separated from it by an
extensive and deep lagoon; this bank of sand rests on coral-rock, and
undoubtedly was originally a living reef. North of Bolabola lies the
atoll of _Toubai_ (Motou-iti of the “‘Coquille’s’ Atlas”) which is
coloured dark blue; the other islands, surrounded by barrier-reefs, are
pale blue; three of them are represented in Figures 3, 4, and 5, in
Plate I. There are three low coral-groups lying a little E. of the
Society Archipelago, and almost forming part of it, namely
_Bellinghausen_, which is said by Kotzebue (“Second Voyage,” volume
ii., page 255), to be a lagoon-island; _Mopeha_, which, from Cook’s
description (“Second Voyage,” book iii., chapter i.), no doubt is an
atoll; and the _Scilly_ Islands, which are said by Wallis (“Voyage,”
chapter ix.) to form a _group_ of _low_ islets and shoals, and,
therefore, probably, they compose an atoll: the two former have been
coloured blue, but not the latter.
MENDANA or MARQUESAS Group.—These islands are entirely without reefs,
as may be seen in Krusenstern’s Atlas, making a remarkable contrast
with the adjacent group of the Society Islands. Mr. F.D. Bennett has
given some account of this group, in the seventh volume of the
“Geographical Journal”. He informs me that all the islands have the
same general character, and that the water is very deep close to their
shores. He visited three of them, namely, _Dominicana_, _Christiana_,
and _Roapoa;_ their beaches are strewed with rounded masses of coral,
and although no regular reefs exist, yet the shore is in many places
lined by coral-rock, so that a boat grounds on this formation. Hence
these islands ought probably to come within the class of fringed
islands and be coloured red; but as I am determined to err on the
cautious side, I have left them uncoloured.
COOK or HARVEY and AUSTRAL ISLAND.—_Palmerston_ Island is minutely
described as an atoll by Captain Cook during his voyage in 1774;
coloured blue. _Aitutaki_ was partially surveyed by the “Beagle” (see
map accompanying “Voyages of ‘Adventure’ and ‘Beagle’”); the land is
hilly, sloping gently to the beach; the highest point is 360 feet; on
the southern side the reef projects five miles from the land: off this
point the “Beagle” found no bottom with 270 fathoms: the reef is
surmounted by many low coral-islets. Although within the reef the water
is exceedingly shallow, not being more than a few feet deep, as I am
informed by the Rev. J. Williams, nevertheless, from the great
extension of this reef into a profoundly deep ocean, this island
probably belongs, on the principle lately adverted to, to the barrier
class, and I have coloured it pale blue; although with much
hesitation.—_Manouai_ or _Harvey_ Island. The highest point is about
fifty feet: the Rev. J. Williams informs me that the reef here,
although it lies far from the shore, is less distant than at Aitutaki,
but the water within the reef is rather deeper: I have also coloured
this pale blue with many doubts.—Round _Mitiaro_ Island, as I am
informed by Mr. Williams, the reef is attached to the shore; coloured
red. —_Mauki_ or Maouti; the reef round this island (under the name of
Parry Island, in the “Voyage of H.M.S. ‘Blonde’,” page 209) is
described as a coral-flat, only fifty yards wide, and two feet under
water. This statement has been corroborated by Mr. Williams, who calls
the reef attached; coloured red.—_Aitu_, or Wateeo; a moderately
elevated hilly island, like the others of this group. The reef is
described in Cook’s “Voyage,” as attached to the shore, and about one
hundred yards wide; coloured red.—_Fenoua-iti;_ Cook describes this
island as very low, not more than six or seven feet high (volume i.,
book ii., chapter iii, 1777); in the chart published in the
“‘Coquille’s’ Atlas,” a reef is engraved close to the shore: this
island is not mentioned in the list given by Mr. Williams (page 16) in
the “Narrative of Missionary Enterprise;” nature doubtful. As it is so
near Atiu, it has been unavoidably coloured red.— _Rarotonga;_ Mr.
Williams informs me that it is a lofty basaltic island with an attached
reef; coloured red.—There are three islands, _Rourouti_, _Roxburgh_,
and _Hull_, of which I have not been able to obtain any account, and
have left them uncoloured. Hull Island, in the French chart, is written
with small letters as being low.—_Mangaia;_ height about three hundred
feet; “the surrounding reef joins the shore” (Williams, “Narrative,”
page 18); coloured red.—_Rimetara;_ Mr. Williams informs me that the
reef is rather close to the shore; but, from information given me by
Mr. Ellis, the reef does not appear to be quite so closely attached to
it as in the foregoing cases: the island is about three hundred feet
high (“Naut. Mag.” 1839, page 738); coloured red.—_Rurutu;_ Mr.
Williams and Mr. Ellis inform me that this island has an attached reef;
coloured red. It is described by Cook under the name of Oheteroa: he
says it is not surrounded, like the neighbouring islands by a reef; he
must have meant a distant reef.—_Toubouai;_ in Cook’s chart (“Second
Voyage,” volume ii., page 2) the reef is laid down in part one mile,
and in part two miles from the shore. Mr. Ellis (“Polynes. Res.” volume
iii., page 381) says the low land round the base of the island is very
extensive; and this gentleman informs me that the water within the reef
appears deep; coloured blue.—_Raivaivai_, or Vivitao; Mr. Williams
informs me that the reef is here distant: Mr. Ellis, however, says that
this is certainly not the case on one side of the island; and he
believes that the water within the reef is not deep; hence I have left
it uncoloured.—_Lancaster_ Reef, described in “Naut. Mag.” 1833 (page
693), as an extensive crescent-formed coral-reef. I have not coloured
it.—_Rapa_, or Oparree; from the accounts given of it by Ellis and
Vancouver, there does not appear to be any reef.—_I. de Bass_ is an
adjoining island, of which I cannot find any account.—_Kemin_ Island;
Krusenstern seems hardly to know its position, and gives no further
particulars.
ISLANDS BETWEEN _the Low and Gilbert Archipelagoes_.
_Caroline_ Island (10° S., 150° W.) is described by Mr. F.D. Bennett
(“Geographical Journal”, volume vii., page 225) as containing a fine
lagoon; coloured blue.—_Flint_ Island (11° S., 151° W.); Krusenstern
believes that it is the same with _Peregrino_, which is described by
Quiros (Burney’s “Chron. Hist.” volume ii., page 283) as “a cluster of
small islands connected by a reef, and forming a lagoon in the middle;”
coloured blue.—_Wostock_ is an island a little more than half a mile in
diameter, and apparently quite flat and low, and was discovered by
Bellinghausen; it is situated a little west of Caroline Island, but it
is not placed on the French charts; I have not coloured it, although I
entertain little doubt from the chart of Bellinghausen, that it
originally contained a small lagoon.—_Penrhyn_ Island (9° S., 158° W.);
a plan of it in the “Atlas of the First Voyage” of Kotzebue, shows that
it is an atoll; blue.— _Starbuck_ Island (5° S., 156° W.) is described
in Byron’s “Voyage in the ‘Blonde’” (page 206) as formed of a flat
coral-rock, with no trees; the height not given; not coloured.—_Malden_
Island (4° S., 154° W.); in the same voyage (page 205) this island is
said to be of coral formation, and no part above forty feet high; I
have not ventured to colour it, although, from being of
coral-formation, it is probably fringed; in which case it should be
red.—_Jarvis_, or _Bunker_ Island (0° 20′ S., 160° W.) is described by
Mr. F.D. Bennett (“Geographical Journal”, volume vii., page 227) as a
narrow, low strip of coral-formation; not coloured.—_Brook_, is a small
low island between the two latter; the position, and perhaps even the
existence of it is doubtful; not coloured.—_Pescado_ and _Humphrey_
Islands; I can find out nothing about these islands, except that the
latter appears to be small and low; not coloured.—_Rearson_, or Grand
Duke Alexander’s (10 S., 161° W.); an atoll, of which a plan is given
by Bellinghausen; blue.— _Souvoroff_ Islands (13° S., 163° W.); Admiral
Krusenstern, in the most obliging manner, obtained for me an account of
these islands from Admiral Lazareff, who discovered them. They consist
of five very low islands of coral-formation, two of which are connected
by a reef, with deep water close to it. They do not surround a lagoon,
but are so placed that a line drawn through them includes an oval
space, part of which is shallow; these islets, therefore, probably once
(as is the case with some of the islands in the Caroline Archipelago)
formed a single atoll; but I have not coloured them.—_Danger_ Island
(10° S., 166° W.); described as low by Commodore Byron, and more lately
surveyed by Bellinghausen; it is a small atoll with three islets on it;
blue.—_Clarence_ Island (9° S., 172° W.); discovered in the “Pandora”
(G. Hamilton’s “Voyage,” page 75): it is said, “in running along the
land, we saw several canoes crossing the _lagoons;_” as this island is
in the close vicinity of other low islands, and as it is said, that the
natives make reservoirs of water in old cocoa-nut trees (which shows
the nature of the land), I have no doubt it is an atoll, and have
coloured it blue. _York_ Island (8° S., 172° W.) is described by
Commodore Byron (chapter x. of his “Voyage”) as an atoll;
blue.—_Sydney_ Island (4° S., 172° W.) is about three miles in
diameter, with its interior occupied by a lagoon (Captain Tromelin,
“Annal. Marit.” 1829, page 297); blue.—_Phœnix_ Island (4° S., 171° W.)
is nearly circular, low, sandy, not more than two miles in diameter,
and very steep outside (Tromelin, “Annal. Marit.” 1829, page 297); it
may be inferred that this island originally contained a lagoon, but I
have not coloured it.—_New Nantucket_ (0° 15′ N., 174° W.). From the
French chart it must be a low island; I can find nothing more about it
or about _Mary_ Island; both uncoloured.—_Gardner_ Island (5° S., 174°
W.) from its position is certainly the same as _Kemin_ Island described
(Krusenstern, page 435, Appen. to Mem., published 1827) as having a
lagoon in its centre; blue.
ISLANDS SOUTH _of the Sandwich Archipelago_.
_Christmas_ Island (2° N., 157° W.). Captain Cook, in his “Third
Voyage” (Volume ii., chapter x.), has given a detailed account of this
atoll. The breadth of the islets on the reef is unusually great, and
the sea near it does not deepen so suddenly as is generally the case.
It has more lately been visited by Mr. F.D. Bennett (“Geographical
Journal,” volume vii., page 226); and he assures me that it is low and
of coral-formation: I particularly mention this, because it is engraved
with a capital letter, signifying a high island, in D’Urville and
Lottin’s chart. Mr. Couthouy, also, has given some account of it
(“Remarks,” page 46) from the Hawaiian “Spectator”; he believes it has
lately undergone a small elevation, but his evidence does not appear to
me satisfactory; the deepest part of the lagoon is said to be only ten
feet; nevertheless, I have coloured it blue.—_Fanning_ Island (4° N.,
158° W.) according to Captain Tromelin (“Ann. Maritim.” 1829, page
283), is an atoll: his account as observed by Krusenstern, differs from
that given in Fanning’s “Voyage” (page 224), which, however, is far
from clear; coloured blue.— _Washington_ Island (4° N., 159° W.) is
engraved as a low island in D’Urville’s chart, but is described by
Fanning (page 226) as having a much greater elevation than Fanning
Island, and hence I presume it is not an atoll; not coloured.—_Palmyra_
Island (6° N., 162° W.) is an atoll divided into two parts
(Krusenstern’s “Mem. Suppl.” page 50, also Fanning’s “Voyage,” page
233); blue.—_Smyth’s_ or Johnston’s Islands (17° N., 170° W.). Captain
Smyth, R.N., has had the kindness to inform me that they consist of two
very low, small islands, with a dangerous reef off the east end of
them. Captain Smyth does not recollect whether these islets, together
with the reef, surrounded a lagoon; uncoloured.
SANDWICH ARCHIPELAGO.—_Hawaii;_ in the chart in Freycinet’s “Atlas,”
small portions of the coast are fringed by reefs; and in the
accompanying “Hydrog. Memoir,” reefs are mentioned in several places,
and the coral is said to injure the cables. On one side of the islet of
Kohaihai there is a bank of sand and coral with five feet water on it,
running parallel to the shore, and leaving a channel of about fifteen
feet deep within. I have coloured this island red, but it is very much
less perfectly fringed than others of the group.—_Maui;_ in Freycinet’s
chart of the anchorage of Raheina, two or three miles of coast are seen
to be fringed; and in the “Hydrog. Memoir,” “banks of coral along
shore” are spoken of. Mr. F.D. Bennett informs me that the reefs, on an
average, extend about a quarter of a mile from the beach; the land is
not very steep, and outside the reefs the sea does not become deep very
suddenly; coloured red.—_Morotoi_, I presume, is fringed: Freycinet
speaks of the breakers extending along the shore at a little distance
from it. From the chart, I believe it is fringed; coloured red.—_Oahu;_
Freycinet, in his “Hydrog. Memoir,” mentions some of the reefs. Mr.
F.D. Bennett informs me that the shore is skirted for forty or fifty
miles in length. There is even a harbour for ships formed by the reefs,
but it is at the mouth of a valley; red.—_Atooi_, in La Peyrouse’s
charts, is represented as fringed by a reef, in the same manner as Oahu
and Morotoi; and this, as I have been informed by Mr. Ellis, on part at
least of the shore, is of coral-formation: the reef does not leave a
deep channel within; red.—_Oneehow;_ Mr. Ellis believes that this
island is also fringed by a coral-reef: considering its close proximity
to the other islands, I have ventured to colour it red. I have in vain
consulted the works of Cook, Vancouver, La Peyrouse, and Lisiansky, for
any satisfactory account of the small islands and reefs, which lie
scattered in a N.W. line prolonged from the Sandwich group, and hence
have left them uncoloured, with one exception; for I am indebted to Mr.
F.D. Bennett for informing me of an atoll-formed reef, in latitude 28°
22′, longitude 178° 30′ W., on which the “Gledstanes” was wrecked in
1837. It is apparently of large size, and extends in a N.W. and S.E.
line: very few islets have been formed on it. The lagoon seems to be
shallow; at least, the deepest part which was surveyed was only three
fathoms. Mr. Couthouy (“Remarks,” page 38) describes this island under
the name of _Ocean_ island. Considerable doubts should be entertained
regarding the nature of a reef of this kind, with a very shallow
lagoon, and standing far from any other atoll, on account of the
possibility of a crater or flat bank of rock lying at the proper depth
beneath the surface of the water, thus affording a foundation for a
ring-formed coral-reef. I have, however, thought myself compelled, from
its large size and symmetrical outline, to colour it blue.
SAMOA or NAVIGATOR GROUP.—Kotzebue, in his “Second Voyage,” contrasts
the structure of these islands with many others in the Pacific, in not
being furnished with harbours for ships, formed by distant coral-reefs.
The Rev. J. Williams, however, informs me, that coral-reefs do occur in
irregular patches on the shores of these islands; but that they do not
form a continuous band, as round Mangaia, and other such perfect cases
of fringed islands. From the charts accompanying La Peyrouse’s
“Voyage,” it appears that the north shore of _Savaii_, _Maouna_,
_Orosenga_, and _Mannua_, are fringed by reefs. La Peyrouse, speaking
of Maouna (page 126), says that the coral-reef surrounding its shores,
almost touches the beach; and is breached in front of the little coves
and streams, forming passages for canoes, and probably even for boats.
Further on (page 159), he extends the same observation to all the
islands which he visited. Mr. Williams in his “Narrative,” speaks of a
reef going round a small island attached to _Oyolava_, and returning
again to it: all these islands have been coloured red.—A chart of
_Rose_ Island, at the extreme west end of the group, is given by
Freycinet, from which I should have thought that it had been an atoll;
but according to Mr. Couthouy (“Remarks,” page 43), it consists of a
reef, only a league in circuit, surmounted by a very few low islets;
the lagoon is very shallow, and is strewed with numerous large boulders
of volcanic rock. This island, therefore, probably consists of a bank
of rock, a few feet submerged, with the outer margin of its upper
surface fringed with reefs; hence it cannot be properly classed with
atolls, in which the foundations are always supposed to lie at a depth,
greater than that at which the reef-constructing polypifers can live;
not coloured.
_Beveridge Reef_, 20° S., 167° W., is described in the “Naut. Mag.”
(May 1833, page 442) as ten miles long in a N. and S. line, and eight
wide; “in the inside of the reef there appears deep water;” there is a
passage near the S.W. corner: this therefore seems to be a submerged
atoll, and is coloured blue.
_Savage_ Island, 19° S., 170° W., has been described by Cook and
Forster. The younger Forster (volume ii., page 163) says it is about
forty feet high: he suspects that it contains a low plain, which
formerly was the lagoon. The Rev. J. Williams informs me that the reef
fringing its shores, resembles that round Mangaia; coloured red.
FRIENDLY ARCHIPELAGO. _Pylstaart_ Island. Judging from the chart in
Freycinet’s “Atlas,” I should have supposed that it had been regularly
fringed; but as nothing is said in the “Hydrog. Memoir” (or in the
“Voyage” of Tasman, the discoverer) about coral-reefs, I have left it
uncoloured.—_Tongatabou:_ In the “Atlas of the Voyage of the
‘Astrolabe’,” the whole south side of the island is represented as
narrowly fringed by the same reef which forms an extensive platform on
the northern side. The origin of this latter reef, which might have
been mistaken for a barrier-reef, has already been attempted to be
explained, when giving the proofs of the recent elevation of this
island.— In Cook’s charts the little outlying island also of _Eoaigee_,
is represented as fringed; coloured red.—_Eoua_. I cannot make out from
Captain Cook’s charts and descriptions, that this island has any reef,
although the bottom of the neighbouring sea seems to be corally, and
the island itself is formed of coral-rock. Forster, however, distinctly
(“Observations,” page 14) classes it with high islands having reefs,
but it certainly is not encircled by a barrier-reef and the younger
Forster (“Voyage,” volume i., page 426) says, that “a bed of
coral-rocks surrounded the coast towards the landing-place.” I have
therefore classed it with the fringed islands and coloured it red. The
several islands lying N.W. of Tongatabou, namely _Anamouka_, _Komango_,
_Kotou_, _Lefouga_, _Foa_, &c., are seen in Captain Cook’s chart to be
fringed by reefs, in several of them are connected together. From the
various statements in the first volume of Cook’s “Third Voyage,” and
especially in the fourth and sixth chapters, it appears that these
reefs are of coral-formation, and certainly do not belong to the
barrier class; coloured red.—_Toufoua_ & _Kao_, forming the western
part of the group, according to Forster have no reefs; the former is an
active volcano.—_Vavao_. There is a chart of this singularly formed
island, by Espinoza: according to Mr. Williams it consists of
coral-rock: the Chevalier Dillon informs me that it is not fringed; not
coloured. Nor are the islands of _Latte_ and _Amargura_, for I have not
seen plans on a large scale of them, and do not know whether they are
fringed.
_Niouha_, 16° S., 174° W., or _Keppel_ Island of Wallis, or _Cocos_
Island. From a view and chart of this island given in Wallis’s “Voyage”
(4to edition) it is evidently encircled by a reef; coloured blue: it is
however remarkable that _Boscawen_ Island, immediately adjoining, has
no reef of any kind; uncoloured.
_Wallis Island_, 13° S., 176° W., a chart and view of this island in
Wallis’s “Voyage” (4to edition) shows that it is encircled. A view of
it in the “Naut. Mag.” July 1833, page 376, shows the same fact; blue.
_Alloufatou_, or _Horn_ Island, _Onouafu_, or _Proby_ Island, and
_Hunter_ Islands, lie between the Navigator and Fidji groups. I can
find no distinct accounts of them.
FIDJI or VITI GROUP.—The best chart of the numerous islands of this
group, will be found in the “Atlas of the ‘Astrolabe’s’ Voyage.” From
this, and from the description given in the “Hydrog. Memoir,”
accompanying it, it appears that many of these islands are bold and
mountainous, rising to the height of between 3,000 and 4,000 feet. Most
of the islands are surrounded by reefs, lying far from the land, and
outside of which the ocean appears very deep. The “Astrolabe” sounded
with ninety fathoms in several places about a mile from the reefs, and
found no bottom. Although the depth within the reef is not laid down,
it is evident from several expressions, that Captain D’Urville believes
that ships could anchor within, if passages existed through the outer
barriers. The Chevallier Dillon informs me that this is the case: hence
I have coloured this group blue. In the S.E. part lies _Batoa_, or
_Turtle_ Island of Cook (“Second Voyage,” volume ii., page 23, and
chart, 4to edition) surrounded by a coral-reef, “which in some places
extends two miles from the shore;” within the reef the water appears to
be deep, and outside it is unfathomable; coloured pale blue. At the
distance of a few miles, Captain Cook (Ibid., page 24) found a circular
coral-reef, four or five leagues in circuit, with deep water within;
“in short, the bank wants only a few little islets to make it exactly
like one of the half-drowned isles so often mentioned,”—namely, atolls.
South of Batoa, lies the high island of _Ono_, which appears in
Bellinghausen’s “Atlas” to be encircled; as do some other small islands
to the south; coloured pale blue; near Ono, there is an annular reef,
quite similar to the one just described in the words of Captain Cook;
coloured dark blue.
_Rotoumah_, 13° S., 179° E.—From the chart in Duperrey’s “Atlas,” I
thought this island was encircled, and had coloured it blue, but the
Chevallier Dillon assures me that the reef is only a shore or fringing
one; red.
_Independence_ Island, 10° S., 179° E., is described by Mr. G. Bennett,
(“United Service Journal,” 1831, part ii., page 197) as a low island of
coral-formation, it is small, and does not appear to contain a lagoon,
although an opening through the reef is referred to. A lagoon probably
once existed, and has since been filled up; left uncoloured.
ELLICE GROUP.—_Oscar_, _Peyster_, and _Ellice_ Islands are figured in
Arrowsmith’s “Chart of the Pacific” (corrected to 1832) as atolls, and
are said to be very low; blue.—_Nederlandisch_ Island. I am greatly
indebted to the kindness of Admiral Krusenstern, for sending me the
original documents concerning this island. From the plans given by
Captains Eeg and Khremtshenko, and from the detailed account given by
the former, it appears that it is a narrow coral-island, about two
miles long, containing a small lagoon. The sea is very deep close to
the shore, which is fronted by sharp coral-rocks. Captain Eeg compares
the lagoon with that of other coral-islands; and he distinctly says,
the land is “very low.” I have therefore coloured it blue. Admiral
Krusenstern (“Memoir on the Pacific,” Append., 1835) states that its
shores are eighty feet high; this probably arose from the height of the
cocoa-nut trees, with which it is covered, being mistaken for land.
—_Gran Cocal_ is said in Krusenstern’s “Memoir,” to be low, and to be
surrounded by a reef; it is small, and therefore probably once
contained a lagoon; uncoloured.—_St. Augustin_. From a chart and view
of it, given in the “Atlas of the ‘Coquille’s’ Voyage,” it appears to
be a small atoll, with its lagoon partly filled up; coloured blue.
GILBERT GROUP.—The chart of this group, given in the “Atlas of the
‘Coquille’s’ Voyage,” at once shows that it is composed of ten well
characterised atolls. In D’Urville and Lottin’s chart, _Sydenham_ is
written with a capital letter, signifying that it is high; but this
certainly is not the case, for it is a perfectly characterised atoll,
and a sketch, showing how low it is, is given in the “‘Coquille’s’
Atlas.” Some narrow strip-like reefs project from the southern side of
_Drummond_ atoll, and render it irregular. The southern island of the
group is called _Chase_ (in some charts, _Rotches_); of this I can find
no account, but Mr. F.D. Bennett discovered (“Geographical Journal”,
volume vii., page 229), a low extensive island in nearly the same
latitude, about three degrees westward of the longitude assigned to
Rotches, but very probably it is the same island. Mr. Bennett informs
me that the man at the masthead reported an appearance of lagoon-water
in the centre; and, therefore, considering its position, I have
coloured it blue. —_Pitt_ Island, at the extreme northern point of the
group, is left uncoloured, as its exact position and nature is not
known.—_Byron_ Island, which lies a little to the eastward, does not
appear to have been visited since Commodore Byron’s voyage, and it was
then seen only from a distance of eighteen miles; it is said to be low;
uncoloured.
_Ocean_, _Pleasant_, and _Atlantic_ Islands all lie considerably to the
west of the Gilbert group: I have been unable to find any distinct
account of them. Ocean Island is written with small letters in the
French chart, but in Krusenstern’s “Memoir” it is said to be high.
MARSHALL GROUP.—We are well acquainted with this group from the
excellent charts of the separate islands, made during the two voyages
of Kotzebue: a reduced one of the whole group may be easily seen in
Krusenstern’s “Atlas,” and in Kotzebue’s “Second Voyage.” The group
consists (with the exception of two _little_ islands which probably
have had their lagoon filled up) of a double row of twenty-three large
and well-characterised atolls, from the examination of which Chamisso
has given us his well-known account of coral-formations. I include
_Gaspar-Rico_, or _Cornwallis_ Island in this group, which is described
by Chamisso (Kotzebue’s “First Voyage,” volume iii., page 179) “as a
low sickle-formed group, with mould only on the windward side.” Gaspard
Island is considered by some geographers as a distinct island lying
N.E. of the group, but it is not entered in the chart by Krusenstern;
left uncoloured. In the S.W. part of this group lies _Baring_ Island,
of which little is known (see Krusenstern’s “Appendix,” 1835, page
149). I have left it uncoloured; but _Boston_ Island I have coloured
blue, as it is described (Ibid.) as consisting of fourteen small
islands, which, no doubt, enclose a lagoon, as represented in a chart
in the “‘Coquille’s’ Atlas.”—Two islands, _Aur Kawen_ and _Gaspar
Rico_, are written in the French chart with capital letters; but this
is an error, for from the account given by Chamisso in Kotzebue’s
“First Voyage,” they are certainly low. The nature, position, and even
existence, of the shoals and small islands north of the Marshall group,
are doubtful.
NEW HEBRIDES.—Any chart, on even a small scale, of these islands, will
show that their shores are almost without reefs, presenting a
remarkable contrast with those of New Caledonia on the one hand, and
the Fidji group on the other. Nevertheless, I have been assured by Mr.
G. Bennett, that coral grows vigorously on their shores; as indeed,
will be further shown in some of the following notices. As, therefore,
these islands are not encircled, and as coral grows vigorously on their
shores, we might almost conclude, without further evidence, that they
were fringed, and hence I have applied the red colour with rather
greater freedom than in other instances.—_Matthew’s Rock_, an active
volcano, some way south of the group (of which a plan is given in the
“Atlas of the ‘Astrolabe’s’ Voyage”) does not appear to have reefs of
any kind about it.—_Annatom_, the southernmost of the Hebrides; from a
rough woodcut given in the “United Service Journal” (1831, part iii.,
page 190), accompanying a paper by Mr. Bennett, it appears that the
shore is fringed; coloured red.—_Tanna_. Forster, in his “Observations”
(page 22), says Tanna has on its shores coral-rock and madrepores; and
the younger Forster, in his account (volume ii., page 269) speaking of
the harbour says, the whole S.E. side consists of coral-reefs, which
are overflowed at high-water; part of the southern shore in Cook’s
chart is represented as fringed; coloured red.—_Immer_ is described
(“United Service Journal,” 1831, part iii., page 192) by Mr. Bennett as
being of moderate elevation, with cliffs appearing like sandstone:
coral grows in patches on its shore, but I have not coloured it; and I
mention these facts, because Immer might have been thought from
Forster’s classification (“Observations,” page 14), to have been a low
island or even an atoll.— _Erromango_ Island; Cook (“Second Voyage,”
volume ii., page 45, 4to edition) speaks of rocks everywhere _lining_
the coast, and the natives offered to haul his boat over the breakers
to the sandy beach: Mr. Bennett, in a letter to the Editor of the
“Singapore Chron.,” alludes to the _reefs_ on its shores. It may, I
think, be safely inferred from these passages that the shore is fringed
in parts by coral-reefs; coloured red.—_Sandwich_ Island. The east
coast is said (Cook’s “Second Voyage,” volume ii., page 41) to be low,
and to be guarded by a chain of breakers. In the accompanying chart it
is seen to be fringed by a reef; coloured red.—_Mallicollo_; Forster
speaks of the reef-bounded shore: the reef is about thirty yards wide,
and so shallow that a boat cannot pass over it. Forster also
(“Observations,” page 23) says, that the rocks of the sea-shore consist
of madrepore. In the plan of Sandwich harbour, the headlands are
represented as fringed; coloured red.—_Aurora_ and _Pentecost_ Islands,
according to Bougainville, apparently have no reefs; nor has the large
island of _S. Espiritu_, nor _Bligh_ Island or _Banks’_ Islands, which
latter lie to the N.E. of the Hebrides. But in none of these cases,
have I met with any detailed account of their shores, or seen plans on
a large scale; and it will be evident, that a fringing-reef of only
thirty or even a few hundred yards in width, is of so little importance
to navigation, that it will seldom be noticed, excepting by chance; and
hence I do not doubt that several of these islands, now left
uncoloured, ought to be red.
SANTA-CRUZ GROUP.—_Vanikoro_ (Figure 1, Plate I.) offers a striking
example of a barrier-reef: it was first described by the Chevalier
Dillon, in his voyage, and was surveyed in the “Astrolabe”; coloured
pale blue.—_Tikopia_ and _Fataka_ Islands appear, from the descriptions
of Dillon and D’Urville, to have no reefs; _Anouda_ is a low, flat
island, surrounded by cliffs (“‘Astrolabe’ Hydrog.” and Krusenstern,
“Mem.” volume ii., page 432); these are uncoloured. _Toupoua_
(_Otooboa_ of Dillon) is stated by Captain Tromelin (“Annales Marit.”
1829, page 289) to be almost entirely included in a reef, lying at the
distance of two miles from the shore. There is a space of three miles
without any reef, which, although indented with bays, offers no
anchorage from the extreme depth of the water close to the shore:
Captain Dillon also speaks of the reefs fronting this island; coloured
blue.— _Santa-Cruz_. I have carefully examined the works of Carteret,
D’Entrecasteaux, Wilson, and Tromelin, and I cannot discover any
mention of reefs on its shores; left uncoloured.—_Tinakoro_ is a
constantly active volcano without reefs.—_Mendana Isles_ (mentioned by
Dillon under the name of _Mammee_, etc.); said by Krusenstern to be
low, and intertwined with reefs. I do not believe they include a
lagoon; I have left them uncoloured.—_Duff’s_ Islands compose a small
group directed in a N.W. and S.E. band; they are described by Wilson
(page 296, “Miss. Voy.” 4to edition), as formed by bold-peaked land,
with the islands surrounded by coral-reefs, extending about half a mile
from the shore; at a distance of a mile from the reefs he found only
seven fathoms. As I have no reason for supposing there is deep water
within these reefs, I have coloured them red. _Kennedy_ Island, N.E. of
Duff’s. I have been unable to find any account of it.
NEW CALEDONIA.—The great barrier-reefs on the shores of this island
have already been described (Figure 5, Plate II.). They have been
visited by Labillardière, Cook, and the northern point by D’Urville;
this latter part so closely resembles an atoll that I have coloured it
dark blue. The _Loyalty_ group is situated eastward of this island;
from the chart and description given in the “Voyage of the
‘Astrolabe’,” they do not appear to have any reefs; north of this
group, there are some extensive low reefs (called _Astrolabe_ and
_Beaupré_,) which do not seem to be atoll-formed; these are left
uncoloured.
AUSTRALIAN BARRIER-REEF.—The limits of this great reef, which has
already been described, have been coloured from the charts of Flinders
and King. In the northern parts, an atoll-formed reef, lying outside
the barrier, has been described by Bligh, and is coloured dark blue. In
the space between Australia and New Caledonia, called by Flinders the
Corallian Sea, there are numerous reefs. Of these, some are represented
in Krusenstern’s “Atlas” as having an atoll-like structure; namely,
_Bampton_ shoal, _Frederic_, _Vine_ or Horse-shoe, and _Alert_ reefs;
these have been coloured dark blue.
LOUISIADE: the dangerous reefs which front and surround the western,
southern, and northern coasts of this so-called peninsula and
archipelago, seem evidently to belong to the barrier class. The land is
lofty, with a low fringe on the coast; the reefs are distant, and the
sea outside them profoundly deep. Nearly all that is known of this
group is derived from the labours of D’Entrecasteaux and Bougainville:
the latter has represented one continuous reef ninety miles long,
parallel to the shore, and in places as much as ten miles from it;
coloured pale blue. A little distance northward we have the _Laughlan_
Islands, the reefs round which are engraved in the “Atlas of the Voyage
of the ‘Astrolabe’,” in the same manner as in the encircled islands of
the Caroline Archipelago, the reef is, in parts, a mile and a half from
the shore, to which it does not appear to be attached; coloured blue.
At some little distance from the extremity of the Louisiade lies the
_Wells_ reef, described in G. Hamilton’s “Voyage in H.M.S. ‘Pandora’”
(page 100): it is said, “We found we had got embayed in a double reef,
which will soon be an island.” As this statement is only intelligible
on the supposition of the reef being crescent or horse-shoe formed,
like so many other submerged annular reefs, I have ventured to colour
it blue.
SALOMON ARCHIPELAGO: the chart in Krusenstern’s “Atlas” shows that
these islands are not encircled, and as coral appears from the works of
Surville, Bougainville, and Labillardière, to grow on their shores,
this circumstance, as in the case of the New Hebrides, is a presumption
that they are fringed. I cannot find out anything from
D’Entrecasteaux’s “Voyage,” regarding the southern islands of the
group, so have left them uncoloured.—_Malayta_ Island in a rough MS.
chart in the Admiralty has its northern shore fringed.—_Ysabel_ Island,
the N.E. part of this island, in the same chart, is also fringed:
Mendana, speaking (Burney, volume i., page 280) of an islet adjoining
the northern coast, says it is surrounded by reefs; the shores, also of
Port Praslin appear regularly fringed.—_Choiseul_ Island. In
Bougainville’s “Chart of Choiseul Bay,” parts of the shores are fringed
by coral-reefs.— _Bougainville_ Island. According to D’Entrecasteaux
the western shore abounds with coral-reefs, and the smaller islands are
said to be attached to the larger ones by reefs; all the
before-mentioned islands have been coloured red.—_Bouka_ Islands.
Captain Duperrey has kindly informed me in a letter that he passed
close round the northern side of this island (of which a plan is given
in his “Atlas of the ‘Coquille’s’ Voyage”), and that it was “garnie
d’une bande de récifs à fleur d’eau adherentes au rivage;” and he
infers, from the abundance of coral on the islands north and south of
Bouka, that the reef probably is of coral; coloured red.
Off the north coast of the Solomon Archipelago there are several small
groups which are little known; they appear to be low, and of
coral-formation; and some of them probably have an atoll-like
structure; the Chevallier Dillon, however, informs me that this is not
the case with the B. de _Candelaria_.—_Outong Java_, according to the
Spanish navigator, Maurelle, is thus characterised; but this is the
only one which I have ventured to colour blue.
NEW IRELAND.—The shores of the S.W. point of this island and some
adjoining islets, are fringed by reefs, as may be seen in the “Atlases
of the Voyages of the ‘Coquille’ and ‘Astrolabe’.” M. Lesson observes
that the reefs are open in front of each streamlet. The _Duke of
York’s_ Island is also fringed; but with regard to the other parts of
_New Ireland_, _New Hanover_, and the small islands lying northward, I
have been unable to obtain any information. I will only add that no
part of New Ireland appears to be fronted by distant reefs. I have
coloured red only the above specified portions.
NEW BRITAIN and the NORTHERN SHORE of NEW GUINEA.—From the charts in
the “Voyage of the ‘Astrolabe’,” and from the “Hydrog. Memoir,” it
appears that these coasts are entirely without reefs, as are the
_Schouten Islands_, lying close to the northern shore of New Guinea.
The western and south-western parts of New Guinea, will be treated of
when we come to the islands of the East Indian Archipelago.
ADMIRALTY GROUP.—From the accounts by Bougainville, Maurelle,
D’Entrecasteaux, and the scattered notices collected by Horsburgh, it
appears, that some of the many islands composing it, are high, with a
bold outline; and others are very low, small and interlaced with reefs.
All the high islands appear to be fronted by distant reefs rising
abruptly from the sea, and within some of which there is reason to
believe that the water is deep. I have therefore little doubt they are
of the barrier class.—In the southern part of the group we have
_Elizabeth Island_, which is surrounded by a reef at the distance of a
mile; and two miles eastward of it (Krusenstern, “Append.” 1835, page
42) there is a little island containing a lagoon.—Near here, also lies
_Circular-reef_ (Horsburgh, “Direct.” volume i., page 691, 4th
edition), “three or four miles in diameter having deep water inside
with an opening at the N.N.W. part, and on the outside steep to.” I
have from these data, coloured the group pale blue, and _circular-reef_
dark blue.—the _Anachorites_, _Echequier_, and _Hermites_, consist of
innumerable low islands of coral-formation, which probably have
atoll-like forms; but not being able to ascertain this, I have not
coloured them, nor _Durour_ Island, which is described by Carteret as
low.
The CAROLINE ARCHIPELAGO is now well-known, chiefly from the
hydrographical labours of Lutké; it contains about forty groups of
atolls, and three encircled islands, two of which are engraved in
Figures 2 and 7, Plate I. Commencing with the eastern part; the
encircling reef round _Ualen_ appears to be only about half a mile from
the shore; but as the land is low and covered with mangroves (“Voyage
autour du Monde,” par F. Lutké, volume i., page 339), the real margin
has not probably been ascertained. The extreme depth in one of the
harbours within the reef is thirty-three fathoms (see charts in “Atlas
of ‘Coquille’s’ Voyage”), and outside at half a mile distant from the
reef, no bottom was obtained with two hundred and fifty fathoms. The
reef is surmounted by many islets, and the lagoon-like channel within
is mostly shallow, and appears to have been much encroached on by the
low land surrounding the central mountains; these facts show that time
has allowed much detritus to accumulate; coloured pale blue.—
_Pouynipète_, or _Seniavine_. In the greater part of the circumference
of this island, the reef is about one mile and three quarters distant;
on the north side it is five miles off the included high islets. The
reef is broken in several places; and just within it, the depth in one
place is thirty fathoms, and in another, twenty-eight, beyond which, to
all appearance, there was “un porte vaste et sur” (Lutké, volume ii.,
page 4); coloured pale blue.—_Hogoleu_ or _Roug_. This wonderful group
contains at least sixty-two islands, and its reef is one hundred and
thirty-five miles in circuit. Of the islands, only a few, about six or
eight (see “Hydrog. Descrip.” page 428, of the “Voyage of the
‘Astrolabe’,” and the large accompanying chart taken chiefly from that
given by Duperrey) are high, and the rest are all small, low, and
formed on the reef. The depth of the great interior lake has not been
ascertained; but Captain D’Urville appears to have entertained no doubt
about the possibility of taking in a frigate. The reef lies no less
than fourteen miles distant from the northern coasts of the interior
high islands, seven from their western sides, and twenty from the
southern; the sea is deep outside. This island is a likeness on a grand
scale to the Gambier group in the Low Archipelago. Of the groups of
low[1] islands forming the chief part of the Caroline Archipelago, all
those of larger size, have the true atoll-structure (as may be seen in
the “Atlas” by Captain Lutké), and some even of the very small ones, as
_Macaskill_ and _Duperrey_, of which plans are given in the “Atlas of
the ‘Coquille’s’ Voyage.” There are, however, some low small islands of
coral-formation, namely _Ollap_, _Tamatam_, _Bigali_, _Satahoual_,
which do not contain lagoons; but it is probable that lagoons
originally existed, but have since filled up: Lutké (volume ii., page
304) seems to have thought that all the low islands, with only one
exception, contained lagoons. From the sketches, and from the manner in
which the margins of these islands are engraved in the “Atlas of the
Voyage of the ‘Coquille’,” it might have been thought that they were
not low; but by a comparison with the remarks of Lutké (volume ii.,
page 107, regarding Bigali) and of Freycinet (“Hydrog. Memoir
‘L’Uranie’ Voyage,” page 188, regarding Tamatam, Ollap, etc.), it will
be seen that the artist must have represented the land incorrectly. The
most southern island in the group, namely _Piguiram_, is not coloured,
because I have found no account of it. _Nougouor_, or _Monte Verdison_,
which was not visited by Lutké, is described and figured by Mr. Bennett
(“United Service Journal,” January 1832) as an atoll. All the
above-mentioned islands have been coloured blue.
[1] In D’Urville and Lottin’s chart, Peserare is written with capital
letters; but this evidently is an error, for it is one of the low
islets on the reef of Namonouyto (see Lutké’s charts)—a regular atoll.
WESTERN PART OF THE CAROLINE ARCHIPELAGO.—_Fais_ Island is ninety feet
high, and is surrounded, as I have been informed by Admiral Lutké, by a
narrow reef of living coral, of which the broadest part, as represented
in the charts, is only 150 yards; coloured red.— _Philip_ Island., I
believe, is low; but Hunter, in his “Historical Journal,” gives no
clear account of it; uncoloured.—_Elivi;_ from the manner in which the
islets on the reefs are engraved, in the “Atlas of the ‘Astrolabe’s’
Voyage,” I should have thought they were above the ordinary height, but
Admiral Lutké assures me this is not the case: they form a regular
atoll; coloured blue.—_Gouap_ (_Eap_ of Chamisso), is a high island
with a reef (see chart in “Voyage of the ‘Astrolabe’”), more than a
mile distant in most parts from the shore, and two miles in one part.
Captain D’Urville thinks that there would be anchorage (“Hydrog.
Descript. ‘Astrolabe’ Voyage,” page 436) for ships within the reef, if
a passage could be found; coloured pale blue.—_Goulou_, from the chart
in the “‘Astrolabe’s’ Atlas,” appears to be an atoll. D’Urville
(“Hydrog. Descript.” page 437) speaks of the low islets on the reef;
coloured dark blue.
PELEW ISLANDS.—Krusenstern speaks of some of the islands being
mountainous; the reefs are distant from the shore, and there are spaces
within them, and not opposite valleys, with from ten to fifteen
fathoms. According to a MS. chart of the group by Lieutenant Elmer in
the Admiralty, there is a large space within the reef with deepish
water; although the high land does not hold a central position with
respect to the reefs, as is generally the case, I have little doubt
that the reefs of the Pelew Islands ought to be ranked with the barrier
class, and I have coloured them pale blue. In Lieutenant Elmer’s chart
there is a horseshoe-formed shoal, laid down thirteen miles N.W. of
Pelew, with fifteen fathoms within the reef, and some dry banks on it;
coloured dark blue.—_Spanish_, _Martires_, _Sanserot_, _Pulo Anna_ and
_Mariere_ Islands are not coloured, because I know nothing about them,
excepting that according to Krusenstern, the second, third, and fourth
mentioned, are low, placed on coral-reefs, and therefore, perhaps,
contain lagoons; but Pulo Mariere is a little higher.
MARIANA ARCHIPELAGO, or LADRONES.—_Guahan_. Almost the whole of this
island is fringed by reefs, which extend in most parts about a third of
a mile from the land. Even where the reefs are most extensive, the
water within them is shallow. In several parts there is a navigable
channel for boats and canoes within the reefs. In Freycinet’s “Hydrog.
Mem.” there is an account of these reefs, and in the “Atlas,” a map on
a large scale; coloured red.—_Rota_. “L’ile est presque entièrement
entourée des récifs” (page 212, Freycinet’s “Hydrog. Mem.”). These
reefs project about a quarter of a mile from the shore; coloured
red.—_Tinian_. The eastern coast is precipitous, and is without reefs;
but the western side is fringed like the last island; coloured
red.—_Saypan_. The N.E. coast, and likewise the western shores appear
to be fringed; but there is a great, irregular, horn-like reef
projecting far from this side; coloured red.—_Farallon de Medinilla_,
appears so regularly and closely fringed in Freycinet’s charts, that I
have ventured to colour it red, although nothing is said about reefs in
the “Hydrographical Memoir.” The several islands which form the
northern part of the group are volcanic (with the exception perhaps of
Torres, which resembles in form the madreporitic island of Medinilla),
and appear to be without reefs.—_Mangs_, however, is described (by
Freycinet, page 219, “Hydrog.”) from some Spanish charts, as formed of
small islands placed “au milieu des nombreux récifs;” and as these
reefs in the general chart of the group do not project so much as a
mile; and as there is no appearance from a double line, of the
existence of deep water within, I have ventured, although with much
hesitation, to colour them red. Respecting _Folger_ and _Marshall_
Islands which lie some way east of the Marianas, I can find out
nothing, excepting that they are probably low. Krusenstern says this of
Marshall Island; and Folger Island is written with small letters in
D’Urville’s chart; uncoloured.
BONIN or ARZOBISPO GROUP.—_Peel Island_ has been examined by Captain
Beechey, to whose kindness I am much indebted for giving me information
regarding it: “At Port Lloyd there is a great deal of coral; and the
inner harbour is entirely formed by coral-reefs, which extend outside
the port along the coast.” Captain Beechey, in another part of his
letter to me, alludes to the reefs fringing the island in all
directions; but at the same time it must be observed that the surf
washes the volcanic rocks of the coast in the greater part of its
circumference. I do not know whether the other islands of the
Archipelago are fringed; I have coloured Peel Island red.—_Grampus
Island_ to the eastward, does not appear (Meare’s “Voyage,” page 95) to
have any reefs, nor does _Rosario Island_ (from Lutké’s chart), which
lies to the westward. Respecting the few other islands in this part of
the sea, namely the _Sulphur Islands_, with an active volcano, and
those lying between Bonin and Japan (which are situated near the
extreme limit in latitude, at which reefs are formed), I have not been
able to find any clear account.
WEST END OF NEW GUINEA.—_Port Dory_. From the charts in the “Voyage of
the ‘Coquille’,” it would appear that the coast in this part is fringed
by coral-reefs; M. Lesson, however, remarks that the coral is sickly;
coloured red.—_Waigiou_. A considerable portion of the northern shores
of these islands is seen in the charts (on a large scale) in
Freycinet’s “Atlas” to be fringed by coral-reefs. Forrest (page 21,
“Voyage to New Guinea”) alludes to the coral-reefs lining the heads of
Piapis Bay; and Horsburgh (volume ii., page 599, 4th edition), speaking
of the islands in Dampier Strait, says “sharp coral-rocks line their
shores;” coloured red.—In the sea north of these islands, we have
_Guedes_ (or _Freewill_, or _St. David’s_), which from the chart given
in the 4to edition of Carteret’s “Voyage,” must be an atoll.
Krusenstern says the islets are very low; coloured blue.—_Carteret’s
Shoals_, in 2° 53′ N., are described as circular, with stony points
showing all round, with deeper water in the middle; coloured
blue.—_Aiou;_ the plan of this group, given in the “Atlas of the Voyage
of the ‘Astrolabe’,” shows that it is an atoll; and, from a chart in
Forrest’s “Voyage,” it appears that there is twelve fathoms within the
circular reef; coloured blue.—The S.W. coast of New Guinea appears to
be low, muddy, and devoid of reefs. The _Arru_, _Timor laut_, and
_Tenimber_ groups have lately been examined by Captain Kolff, the MS.
translation of which, by Mr. W. Earl, I have been permitted to read,
through the kindness of Captain Washington, R.N. These islands are
mostly rather low, and are surrounded by distant reefs (the Ki Islands,
however, are lofty, and, from Mr. Stanley’s survey, appear without
reefs); the sea in some parts is shallow, in others profoundly deep (as
near Larrat). From the imperfection of the published charts, I have
been unable to decide to which class these reefs belong. From the
distance to which they extend from the land, where the sea is very
deep, I am strongly inclined to believe they ought to come within the
barrier class, and be coloured blue; but I have been forced to leave
them uncoloured.—The last-mentioned groups are connected with the east
end of Ceram by a chain of small islands, of which the small groups of
_Ceram-laut_, _Goram_ and _Keffing_ are surrounded by very extensive
reefs, projecting into deep water, which, as in the last case, I
strongly suspect belong to the barrier class; but I have not coloured
them. From the south side of Keffing, the reefs project five miles
(Windsor Earl’s “Sailing Direct. for the Arafura Sea,” page 9).
CERAM.—In various charts which I have examined, several parts of the
coast are represented as fringed by reefs.—_Manipa_ Island, between
Ceram and Bourou, in an old MS. chart in the Admiralty, is fringed by a
very irregular reef, partly dry at low water, which I do not doubt is
of coral-formation; both islands coloured red.—_Bourou;_ parts of this
island appear fringed by coral-reefs, namely, the eastern coast, as
seen in Freycinet’s chart; and _Cajeli Bay_, which is said by Horsburgh
(volume ii., page 630) to be lined by coral-reefs, that stretch out a
little way, and have only a few feet water on them. In several charts,
portions of the islands forming the AMBOINA GROUP are fringed by reefs;
for instance, _Noessa_, _Harenca_, and _Ucaster_, in Freycinet’s
charts. The above-mentioned islands have been coloured red, although
the evidence is not very satisfactory.—North of Bourou the parallel
line of the _Xulla Isles_ extends: I have not been able to find out
anything about them, excepting that Horsburgh (volume ii., page 543)
says that the northern shore is surrounded by a reef at the distance of
two or three miles; uncoloured.—_Mysol Group;_ the Kanary Islands are
said by Forrest (“Voyage,” page 130) to be divided from each other by
deep straits, and are lined with coral-rocks; coloured red.—_Guebe_,
lying between Waigiou and Gilolo, is engraved as if fringed; and it is
said by Freycinet, that all the soundings under five fathoms were on
coral; coloured red.—_Gilolo_. In a chart published by Dalrymple, the
numerous islands on the western, southern (_Batchian_ and the _Strait
of Patientia_), and eastern sides appear fringed by narrow reefs; these
reefs, I suppose, are of coral, for it is said in “Malte Brun” (volume
xii., page 156), “Sur les cotes (of Batchian) comme _dans le plupart_
des iles de cet archipel, il y a de rocs de medrepores d’une beauté et
d’une variété infinies.” Forrest, also (page 50), says Seland, near
Batchian, is a little island with reefs of coral; coloured red.—_Morty_
Island (north of Gilolo). Horsburgh (volume ii., page 506) says the
northern coast is lined by reefs, projecting one or two miles, and
having no soundings close to them; I have left it uncoloured, although,
as in some former cases, it ought probably to be pale blue.—_Celebes_.
The western and northern coasts appear in the charts to be bold and
without reefs. Near the extreme northern point, however, an islet in
the _Straits of Limbe_, and parts of the adjoining shore, appear to be
fringed: the east side of the bay of _Manado_, has deep water, and is
fringed by sand and coral (“‘Astrol.’ Voyage,” Hydrog. Part, pages
453-4); this extreme point, therefore, I have coloured red.—Of the
islands leading from this point to Magindanao, I have not been able to
find any account, except of _Serangani_, which appears surrounded by
narrow reefs; and Forrest (“Voyage,” page 164) speaks of coral on its
shores; I have, therefore, coloured this island red. To the eastward of
this chain lie several islands; of which I cannot find any account,
except of _Karkalang_, which is said by Horsburgh (volume ii., page
504) to be lined by a dangerous reef, projecting several miles from the
northern shore; not coloured.
ISLANDS NEAR TIMOR.—The account of the following islands is taken from
Captain D. Kolff’s “Voyage,” in 1825, translated by Mr. W. Earl, from
the Dutch.—_Lette_ has “reefs extending along shore at the distance of
half a mile from the land.”—_Moa_ has reefs on the S.W. part.—_Lakor_
has a reef lining its shore; these islands are coloured red.—Still more
eastward, _Luan_ has, differently from the last-mentioned islands, an
extensive reef; it is steep outside, and within there is a depth of
twelve feet; from these facts, it is impossible to decide to which
class this island belongs.—_Kissa_, off the point of Timor, has its
“shore fronted by a reef, steep too on the outer side, over which small
proahs can go at the time of high water;” coloured red.—_Timor;_ most
of the points, and some considerable spaces of the northern shore, are
seen in Freycinet’s chart to be fringed by coral-reefs; and mention is
made of them in the accompanying “Hydrog. Memoir;” coloured
red.—_Savu_, S.E. of Timor, appears in Flinders’ chart to be fringed;
but I have not coloured it, as I do not know that the reefs are of
coral.— _Sandalwood_ Island has, according to Horsburgh (volume ii.,
page 607), a reef on its southern shore, four miles distant from the
land; as the neighbouring sea is deep, and generally bold, this
probably is a barrier- reef, but I have not ventured to colour it.
N.W. COAST OF AUSTRALIA.—It appears, in Captain King’s Sailing
Directions (“Narrative of Survey,” volume ii, pages 325-369), that
there are many extensive coral-reefs skirting, often at considerable
distances, the N.W. shores, and encompassing the small adjoining
islets. Deep water, in no instance, is represented in the charts
between these reefs and the land; and, therefore, they probably belong
to the fringing class. But as they extend far into the sea, which is
generally shallow, even in places where the land seems to be somewhat
precipitous; I have not coloured them. Houtman’s Abrolhos (latitude 28°
S. on west coast) have lately been surveyed by Captain Wickham (as
described in “Naut. Mag.” 1841, page 511): they lie on the edge of a
steeply shelving bank, which extends about thirty miles seaward, along
the whole line of coast. The two southern reefs, or islands, enclose a
lagoon-like space of water, varying in depth from five to fifteen
fathoms, and in one spot with twenty-three fathoms. The greater part of
the island has been formed on their inland sides, by the accumulation
of fragments of coral; the seaward face consisting of nearly bare
ledges of rock. Some of the specimens, brought home by Captain Wickham,
contained fragments of marine shells, but others did not; and these
closely resembled a formation at King George’s Sound, principally due
to the action of the wind on calcareous dust, which I shall describe in
a forthcoming part. From the extreme irregularity of these reefs with
their lagoons, and from their position on a bank, the usual depth of
which is only thirty fathoms, I have not ventured to class them with
atolls, and hence have left them uncoloured.—_Rowley Shoals_. These lie
some way from the N.W. coast of Australia: according to Captain King
(“Narrative of Survey,” volume i., page 60), they are of
coral-formation. They rise abruptly from the sea, and Captain King had
no bottom with 170 fathoms close to them. Three of them are
crescent-shaped; they are mentioned by Mr. Lyell, on the authority of
Captain King, with reference to the direction of their open sides. “A
third oval reef of the same group is entirely submerged” (“Principles
of Geology,” book iii. chapter xviii.); coloured blue.—_Scott’s Reefs_,
lying north of Rowley Shoals, are briefly described by Captain Wickham
(“Naut. Mag.” 1841, page 440): they appear to be of great size, of a
circular form, and “with smooth water within, forming probably a lagoon
of great extent.” There is a break on the western side, where there
probably is an entrance: the water is very deep off these reefs;
coloured blue.
Proceeding westward along the great volcanic chain of the East Indian
Archipelago, _Solor Strait_ is represented in a chart published by
Dalrymple from a Dutch MS., as fringed; as are parts of _Flores_, of
_Adenara_, and of _Solor_. Horsburgh speaks of coral growing on these
shores; and therefore I have no doubt that the reefs are of coral, and
accordingly have coloured them red. We hear from Horsburgh (volume ii.,
page 602) that a coral-flat bounds the shores of _Sapy_ Bay. From the
same authority it appears (page 610) that reefs fringe the island of
_Timor-Young_, on the N. shore of Sumbawa; and, likewise (page 600),
that _Bally_ town in _Lombock_, is fronted by a reef, stretching along
the shore at a distance of a hundred fathoms, with channels through it
for boats; these places, therefore, have been coloured red.—_Bally_
Island. In a Dutch MS. chart on a large scale of Java, which was
brought from that island by Dr. Horsfield, who had the kindness to show
it me at the India House, its western, northern, and southern shores
appear very regularly fringed by a reef (see also Horsburgh, volume
ii., page 593); and as coral is found abundantly there, I have not the
least doubt that the reef is of coral, and therefore have coloured it
red.
JAVA.—My information regarding the reefs of this great island is
derived from the chart just mentioned. The greater part of _Madura_ is
represented in it as regularly fringed, and likewise portions of the
coast of Java immediately south of it. Dr. Horsfield informs me that
coral is very abundant near _Sourabaya_. The islets and parts of the N.
coast of Java, west of _Point Buang_, or _Japara_, are fringed by
reefs, said to be of coral. _Lubeck_, or _Bavian_ Islands, lying at
some distance from the shore of Java, are regularly fringed by
coral-reefs. _Carimon Java_ appears equally so, though it is not
directly said that the reefs are of coral; there is a depth between
thirty and forty fathoms round these islands. Parts of the shores of
_Sunda_ Strait, where the water is from forty to eighty fathoms deep,
and the islets near _Batavia_ appear in several charts to be fringed.
In the Dutch chart the southern shore, in the narrowest part of the
island, is in two places fringed by reefs of coral. West of
_Segorrowodee_ Bay, and the extreme S.E. and E. portions are likewise
fringed by coral-reefs; all the above-mentioned places coloured red.
_Macassar Strait_; the east coast of _Borneo_ appears, in most parts,
free from reefs, and where they occur, as on the east coast of
_Pamaroong_, the sea is very shallow; hence no part is coloured. In
_Macassar_ Strait itself, in about latitude 2° S., there are many small
islands with coral-shoals projecting far from them. There are also (old
charts by Dalrymple) numerous little flats of coral, not rising to the
surface of the water, and shelving suddenly from five fathoms to no
bottom with fifty fathoms; they do not appear to have a lagoon-like
structure. There are similar coral-shoals a little farther south; and
in latitude 4° 55′ there are two, which are engraved from modern
surveys, in a manner which might represent an annular reef with deep
water inside: Captain Moresby, however, who was formerly in this sea,
doubts this fact, so that I have left them uncoloured: at the same time
I may remark, that these two shoals make a nearer approach to the
atoll-like structure than any other within the E. Indian Archipelago.
Southward of these shoals there are other low islands and irregular
coral-reefs; and in the space of sea, north of the great volcanic
chain, from Timor to Java, we have also other islands, such as the
_Postillions_, _Kalatoa_, _Tokan-Bessees_, &c., which are chiefly low,
and are surrounded by very irregular and distant reefs. From the
imperfect charts I have seen, I have not been able to decide whether
they belong to the atoll or barrier-classes, or whether they merely
fringe submarine banks, and gently sloping land. In the Bay of _Bonin_,
between the two southern arms of Celebes, there are numerous coral-
reefs; but none of them seem to have an atoll-like structure. I have,
therefore, not coloured any of the islands in this part of the sea; I
think it, however, exceedingly probable that some of them ought to be
blue. I may add that there is a harbour on the S.E. coast of _Bouton_
which, according to an old chart, is formed by a reef, parallel to the
shore, with deep water within; and in the “Voyage of the ‘Coquille’,”
some neighbouring islands are represented with reefs a good way
distant, but I do not know whether with deep water within. I have not
thought the evidence sufficient to permit me to colour them.
SUMATRA.—Commencing with the west coast and outlying islands, _Engano
Island_ is represented in the published chart as surrounded by a narrow
reef, and Napier, in his “Sailing Directions,” speaks of the reef being
of coral (also Horsburgh, volume ii., page 115); coloured red.—_Rat
Island_ (3° 51′ S.) is surrounded by reefs of coral, partly dry at low
water, (Horsburgh, volume ii., page 96).—_Trieste Island_ (4° 2′ S.).
The shore is represented in a chart which I saw at the India House, as
fringed in such a manner, that I feel sure the fringe consists of
coral; but as the island is so low, that the sea sometimes flows quite
over it (Dampier, “Voyage,” volume i., page 474), I have not coloured
it.—_Pulo Dooa_ (latitude 3°). In an old chart it is said there are
chasms in the reefs round the island, admitting boats to the
watering-place, and that the southern islet consists of a mass of sand
and coral.—_Pulo Pisang;_ Horsburgh (volume ii., page 86) says that the
rocky coral-bank, which stretches about forty yards from the shore, is
steep to all round: in a chart, also, which I have seen, the island is
represented as regularly fringed.—_Pulo Mintao_ is lined with reefs on
its west side (Horsburgh, volume ii., page 107).—_Pulo Baniak;_ the
same authority (volume ii., page 105), speaking of a part, says it is
faced with coral-rocks.—_Minguin_ (3° 36′ N.). A coral-reef fronts this
place, and projects into the sea nearly a quarter of a mile (“Notices
of the Indian Arch.” published at Singapore, page 105).—_Pulo Brassa_
(5° 46′ N.). A reef surrounds it at a cable’s length (Horsburgh, volume
ii., page 60). I have coloured all the above-specified points red. I
may here add, that both Horsburgh and Mr. Moor (in the “Notices” just
alluded to) frequently speak of the numerous reefs and banks of coral
on the west coast of Sumatra; but these nowhere have the structure of a
barrier-reef, and Marsden (“History of Sumatra”) states, that where the
coast is flat, the fringing-reefs extend furthest from it. The northern
and southern points, and the greater part of the east coast, are low,
and faced with mud banks, and therefore without coral.
NICOBAR ISLANDS.—The chart represents the islands of this group as
fringed by reefs. With regard to _Great Nicobar_, Captain Moresby
informs me, that it is fringed by reefs of coral, extending between two
and three hundred yards from the shore. The _Northern Nicobars_ appear
so regularly fringed in the published charts, that I have no doubt the
reefs are of coral. This group, therefore, is coloured red.
ANDAMAN ISLANDS.—From an examination of the MS. chart, on a large
scale, of this island, by Captain Arch. Blair, in the Admiralty,
several portions of the coast appear fringed; and as Horsburgh speaks
of coral-reefs being numerous in the vicinity of these islands, I
should have coloured them red, had not some expressions in a paper in
the “Asiatic Researches” (volume iv., page 402) led me to doubt the
existence of reefs; uncoloured.
The coast of _Malacca_, _Tenasserim_ and the coasts northward, appear
in the greater part to be low and muddy: where reefs occur, as in parts
of _Malacca Straits_, and near _Singapore_, they are of the fringing
kind; but the water is so shoal, that I have not coloured them. In the
sea, however, between Malacca and the west coast of Borneo, where there
is a greater depth from forty to fifty fathoms, I have coloured red
some of the groups, which are regularly fringed. The northern _Natunas_
and the _Anambas_ Islands are represented in the charts on a large
scale, published in the “Atlas of the Voyage of the ‘Favourite’,” as
fringed by reefs of coral, with very shoal water within
them.—_Tumbelan_ and _Bunoa_ Islands (1° N.) are represented in the
English charts as surrounded by a very regular fringe.— _St. Barbes_
(0° 15′ N.) is said by Horsburgh (volume ii., page 279) to be fronted
by a reef, over which boats can land only at high water.—The shore of
_Borneo_ at _Tunjong Apee_ is also fronted by a reef, extending not far
from the land (Horsburgh, volume ii., page 468). These places I have
coloured red; although with some hesitation, as the water is shallow. I
might perhaps have added _Pulo Leat_, in Gaspar Strait, _Lucepara_, and
_Carimata;_ but as the sea is confined and shallow, and the reefs not
very regular, I have left them uncoloured.
The water shoals gradually towards the whole west coast of _Borneo:_ I
cannot make out that it has any reefs of coral. The islands, however,
off the northern extremity, and near the S.W. end of _Palawan_, are
fringed by very distant coral-reefs; thus the reefs in the case of
_Balabac_ are no less than five miles from the land; but the sea, in
the whole of this district, is so shallow, that the reefs might be
expected to extend very far from the land. I have not, therefore,
thought myself authorised to colour them. The N.E. point of Borneo,
where the water is very shoal, is connected with Magindanao by a chain
of islands called the _Sooloo Archipelago_, about which I have been
able to obtain very little information; _Pangootaran_, although ten
miles long, entirely consists of a bed of coral-rock (“Notices of E.
Indian Arch.” page 58): I believe from Horsburgh that the island is
low; not coloured.—_Tahow Bank_, in some old charts, appears like a
submerged atoll; not coloured. Forrest (“Voyage,” page 21) states that
one of the islands near Sooloo is surrounded by coral-rocks; but there
is no distant reef. Near the S. end of _Basselan_, some of the islets
in the chart accompanying Forrest’s “Voyage,” appear fringed with
reefs; hence I have coloured, though unwillingly, parts of the Sooloo
group red. The sea between Sooloo and Palawan, near the shoal coast of
Borneo, is interspersed with irregular reefs and shoal patches; not
coloured: but in the northern part of this sea, there are two low
islets, _Cagayanes_ and _Cavilli_, surrounded by extensive coral-reefs;
the breakers round the latter (Horsburgh, volume ii., page 513) extend
five or six miles from a sandbank, which forms the only dry part; these
breakers are steep to outside; there appears to be an opening through
them on one side, with four or five fathoms within: from this
description, I strongly suspect that Cavilli ought to be considered an
atoll; but, as I have not seen any chart of it, on even a moderately
large scale, I have not coloured it. The islets off the northern end of
_Palawan_, are in the same case as those off the southern end, namely
they are fringed by reefs, some way distant from the shore, but the
water is exceedingly shallow; uncoloured. The western shore of Palawan
will be treated of under the head of China Sea.
PHILIPPINE ARCHIPELAGO.—A chart on a large scale of _Appoo shoal_,
which lies near the S.E. coast of Mindoro, has been executed by Captain
D. Ross: it appears atoll-formed, but with rather an irregular outline;
its diameter is about ten miles; there are two well-defined passages
leading into the interior lagoon, which appears open; close outside the
reef all round, there is no bottom with seventy fathoms; coloured
blue.—_Mindoro:_ the N.W. coast is represented in several charts, as
fringed by a reef, and _Luban Island_ is said, by Horsburgh (volume
ii., page 436), to be “lined by a reef.”—_Luzon:_ Mr. Cuming, who has
lately investigated with so much success the Natural History of the
Philippines, informs me, that about three miles of the shore north of
Point St. Jago, is fringed by a reef; as are (Horsburgh, volume ii.,
page 437) the Three Friars off Silanguin Bay. Between Point Capones and
Playa Honda, the coast is “lined by a coral-reef, stretching out nearly
a mile in some places,” (Horsburgh); and Mr. Cuming visited some
fringing- reefs on parts of this coast, namely, near Puebla, Iba, and
Mansinglor. In the neighbourhood of Solon-solon Bay, the shore is lined
(Horsburgh ii., page 439) by coral-reefs, stretching out a great way:
there are also reefs about the islets off Solamague; and as I am
informed by Mr. Cuming, near St. Catalina, and a little north of it.
The same gentleman informs me there are reefs on the S.E. point of this
island in front of Samar, extending from Malalabon to Bulusan. These
appear to be the principal fringing-reefs on the coasts of Luzon; and
they have all been coloured red. Mr. Cuming informs me that none of
them have deep water within; although it appears from Horsburgh that
some few extend to a considerable distance from the shore. Within the
Philippine Archipelago, the shores of the islands do not appear to be
commonly fringed, with the exception of the S. shore of _Masbate_, and
nearly the whole of _Bohol;_ which are both coloured red. On the S.
shore of _Magindanao_, Bunwoot Island is surrounded (according to
Forrest, “Voyage,” page 253), by a coral-reef, which in the chart
appears one of the fringing class. With respect to the eastern coasts
of the whole Archipelago, I have not been able to obtain any account.
BABUYAN ISLANDS.—Horsburgh says (volume ii., page 442), coral-reefs
line the shores of the harbour in Fuga; and the charts show there are
other reefs about these islands. _Camiguin_ has its shore in parts
lined by coral-rock (Horsburgh, page 443); about a mile off shore there
is between thirty and thirty-five fathoms. The plan of Port San Pio
Quinto shows that its shores are fringed with coral; coloured
red.—BABUYAN ISLANDS: Horsburgh, speaking of the southern part of the
group (volume ii., page 445) says the shores of both islands are
fortified by a reef, and through some of the gaps in it, the natives
can pass in their boats in fine weather; the bottom near the land is
coral-rock. From the published charts, it is evident that several of
these islands are most regularly fringed; coloured red. The northern
islands are left uncoloured, as I have been unable to find any account
of them.—FORMOSA. The shores, especially the western one, seem chiefly
composed of mud and sand, and I cannot make out that they are anywhere
lined by reefs; except in a harbour (Horsburgh, volume ii., page 449)
at the extreme northern point: hence, of course, the whole of this
island is left uncoloured. The small adjoining islands are in the same
case.— PATCHOW, or MADJIKO-SIMA GROUPS. _Patchuson_ has been described
by Captain Broughton (“Voy. to the N. Pacific,” page 191); he says, the
boats, with some difficulty, found a passage through the coral-reefs,
which extend along the coast, nearly half a mile off it. The boats were
well sheltered within the reef; but it does not appear that the water
is deep there. Outside the reef the depth is very irregular, varying
from five to fifty fathoms; the form of the land is not very abrupt;
coloured red.—_Taypin-san;_ from the description given (page 195) by
the same author, it appears that a very irregular reef extends, to the
distance of several miles, from the southern island; but whether it
encircles a space of deep water is not evident; nor, indeed, whether
these outlying reefs are connected with those more immediately
adjoining the land; left uncoloured. I may here just add that the shore
of _Kumi_ (lying west of Patchow), has a narrow reef attached to it in
the plan of it, in La Peyrouse’s “Atlas;” but it does not appear in the
account of the voyage that it is of coral; uncoloured.—LOO CHOO. The
greater part of the coast of this moderately hilly island, is skirted
by reefs, which do not extend far from the shore, and which do not
leave a channel of deep water within them, as may be seen in the charts
accompanying Captain B. Hall’s voyage to Loo Choo (see also remarks in
Appendix, pages xxi. and xxv.). There are, however, some ports with
deep water, formed by reefs in front of valleys, in the same manner as
happens at Mauritius. Captain Beechey, in a letter to me, compares
these reefs with those encircling the Society Islands; but there
appears to me a marked difference between them, in the less distance at
which the Loo Choo reefs lie from the land with relation to the
probable submarine inclination, and in the absence of an interior deep
water-moat or channel, parallel to the land. Hence, I have classed
these reefs with fringing-reefs, and coloured them red.—PESCADORES
(west of Formosa). Dampier (volume i., page 416), has compared the
appearance of the land to the southern parts of England. The islands
are interlaced with coral-reefs; but as the water is very shoal, and as
spits of sand and gravel (Horsburgh, volume ii., page 450) extend far
out from them, it is impossible to draw any inferences regarding the
nature of the reefs.
CHINA SEA.—Proceeding from north to south, we first meet the _Pratas
Shoal_ (latitude 20° N.) which, according to Horsburgh (volume ii.,
page 335), is composed of coral, is of a circular form, and has a low
islet on it. The reef is on a level with the water’s edge, and when the
sea runs high, there are breakers mostly all round, “but the water
within seems pretty deep in some places; although steep-to in most
parts outside, there appear to be several parts where a ship might find
anchorage outside the breakers;” coloured blue.—The _Paracells_ have
been accurately surveyed by Captain D. Ross, and charts on a large
scale published: but few low islets have been formed on these shoals,
and this seems to be a general circumstance in the China Sea; the sea
close outside the reefs is very deep; several of them have a
lagoon-like structure; or separate islets (_Prattle_, _Robert_,
_Drummond_, etc.) are so arranged round a moderately shallow space, as
to appear as if they had once formed one large atoll.— _Bombay Shoal_
(one of the Paracells) has the form of an annular reef, and is
“apparently deep within;” it seems to have an entrance (Horsburgh,
volume ii., page 332) on its west side; it is very steep
outside.—_Discovery Shoal_, also is of an oval form, with a lagoon-like
space within, and three openings leading into it, in which there is a
depth from two to twenty fathoms. Outside, at the distance (Horsburgh,
volume ii., page 333) of only twenty yards from the reef, soundings
could not be obtained. The Paracells are coloured blue.—_Macclesfield
Bank:_ this is a coral-bank of great size, lying east of the Paracells;
some parts of the bank are level, with a sandy bottom, but, generally,
the depth is very irregular. It is intersected by deep cuts or
channels. I am not able to perceive in the published charts (its
limits, however, are not very accurately known) whether the central
part is deeper, which I suspect is the case, as in the Great Chagos
Bank, in the Indian Ocean; not coloured.—_Scarborough Shoal:_ this
coral-shoal is engraved with a double row of crosses, forming a circle,
as if there was deep water within the reef: close outside there was no
bottom, with a hundred fathoms; coloured blue.—The sea off the west
coast of Palawan and the northern part of Borneo is strewed with
shoals: _Swallow Shoal_, according to Horsburgh (volume ii., page 431)
“is formed, _like most_ of the shoals hereabouts, of a belt of
coral-rocks, “with a basin of deep water within.”—_Half-Moon Shoal_ has
a similar structure; Captain D. Ross describes it, as a narrow belt of
coral-rock, “with a basin of deep water in the centre,” and deep sea
close outside.—_Bombay Shoal_ appears (Horsburgh, volume ii., page 432)
“to be a basin of smooth water surrounded by breakers.” These three
shoals I have coloured blue.—The _Paraquas Shoals_ are of a circular
form, with deep gaps running through them; not coloured.—A bank
gradually shoaling to the depth of thirty fathoms, extends to a
distance of about twenty miles from the northern part of _Borneo_, and
to thirty miles from the northern part of _Palawan_. Near the land this
bank appears tolerably free from danger, but a little further out it is
thickly studded with coral-shoals, which do not generally rise quite to
the surface; some of them are very steep-to, and others have a fringe
of shoal-water round them. I should have thought that these shoals had
level surfaces, had it not been for the statement made by Horsburgh
“that most of the shoals hereabouts are formed of a belt of coral.”
But, perhaps that expression was more particularly applied to the
shoals further in the offing. If these reefs of coral have a
lagoon-like structure, they should have been coloured blue, and they
would have formed an imperfect barrier in front of Palawan and the
northern part of Borneo. But, as the water is not very deep, these
reefs may have grown up from inequalities on the bank: I have not
coloured them.—The coast of _China_, _Tonquin_, and _Cochin-China_,
forming the western boundary of the China Sea, appear to be without
reefs: with regard to the two last-mentioned coasts, I speak after
examining the charts on a large scale in the “Atlas of the Voyage of
the ‘Favourite’.”
INDIAN OCEAN.—_South Keeling_ has been specially described: nine miles
north of it lies North Keeling, a very small atoll, surveyed by the
“Beagle,” the lagoon of which is dry at low water.—_Christmas Island_,
lying to the east, is a high island, without, as I have been informed
by a person who passed it, any reefs at all.—CEYLON: a space about
eighty miles in length of the south-western and southern shores of
these islands has been described by Mr. Twynam (“Naut. Mag.” 1836,
pages 365 and 518); parts of this space appear to be very regularly
fringed by coral-reefs, which extend from a quarter to half a mile from
the shore. These reefs are in places breached, and afford safe
anchorage for the small trading craft. Outside, the sea gradually
deepens; there is forty fathoms about six miles off shore: this part I
have coloured red. In the published charts of Ceylon there appear to be
fringing-reefs in several parts of the south-eastern shores, which I
have also coloured red.—At Venloos Bay the shore is likewise fringed.
North of Trincomalee there are also reefs of the same kind. The sea off
the northern part of Ceylon is exceedingly shallow; and therefore I
have not coloured the reefs which fringe portions of its shores, and
the adjoining islets, as well as the Indian promontory of _Madura_.
CHAGOS, MALDIVA, and LACCADIVE ARCHIPELAGOES.—These three great groups
which have already been often noticed, are now well-known from the
admirable surveys of Captain Moresby and Lieutenant Powell. The
published charts, which are worthy of the most attentive examination,
at once show that the _Chagos_ and _Maldiva_ groups are entirely formed
of great atolls, or lagoon-formed reefs, surmounted by islets. In the
_Laccadive_ group, this structure is less evident; the islets are low,
not exceeding the usual height of coral-formations (see Lieutenant
Wood’s account, “Geographical Journal”, volume vi., page 29), and most
of the reefs are circular, as may be seen in the published charts; and
within several of them, as I am informed by Captain Moresby, there is
deepish water; these, therefore, have been coloured blue. Directly
north, and almost forming part of this group, there is a long, narrow,
slightly curved bank, rising out of the depths of the ocean, composed
of sand, shells, and decayed coral, with from twenty-three to thirty
fathoms on it. I have no doubt that it has had the same origin with the
other Laccadive banks; but as it does not deepen towards the centre I
have not coloured it. I might have referred to other authorities
regarding these three archipelagoes; but after the publication of the
charts by Captain Moresby, to whose personal kindness in giving me much
information I am exceedingly indebted, it would have been superfluous.
_Sahia de Malha_bank consists of a series of narrow banks, with from
eight to sixteen fathoms on them; they are arranged in a semicircular
manner, round a space about forty fathoms deep, which slopes on the
S.E. quarter to unfathomable depths; they are steep-to on both sides,
but more especially on the ocean-side. Hence this bank closely
resembles in structure, and I may add from Captain Moresby’s
information in composition, the Pitt’s Bank in the Chagos group; and
the Pitt’s Bank, must, after what has been shown of the Great Chagos
Bank, be considered as a sunken, half-destroyed atoll; hence coloured
blue.—_Cargados Carajos Bank_. Its southern portion consists of a
large, curved, coral-shoal, with some low islets on its eastern edge,
and likewise some on the western side, between which there is a depth
of about twelve fathoms. Northward, a great bank extends. I cannot
(probably owing to the want of perfect charts) refer this reef and bank
to any class;—therefore not coloured.—_Ile de Sable_ is a little
island, lying west of C. Carajos, only some toises in height (“Voyage
of the ‘Favourite’,” volume i., page 130); it is surrounded by reefs;
but its structure is unintelligible to me. There are some small banks
north of it, of which I can find no clear account.—_Mauritius_. The
reefs round this island have been described in the chapter on
fringing-reefs; coloured red. —_Rodriguez_. The coral-reefs here are
exceedingly extensive; in one part they project even five miles from
the shore. As far as I can make out, there is no deep-water moat within
them; and the sea outside does not deepen very suddenly. The outline,
however, of the land appears to be (“Life of Sir J. Makintosh,” volume
ii., page 165) hilly and rugged. I am unable to decide whether these
reefs belong to the barrier class; as seems probable from their great
extension, or to the fringing class; uncoloured. —_Bourbon_. The
greater part of the shores of this island are without reefs; but
Captain Carmichael (Hooker’s “Bot. Misc.”) states that a portion,
fifteen miles in length, on the S.E. side, is imperfectly fringed with
coral reefs: I have not thought this sufficient to colour the island.
SEYCHELLES.—The rocky islands of primary formation, composing this
group, rise from a very extensive and tolerably level bank, having a
depth between twenty and forty fathoms. In Captain Owen’s chart, and in
that in the “Atlas of the Voyage of the ‘Favourite’,” it appears that
the east side of _Mahé_ and the adjoining islands of _St. Anne_ and
_Cerf_, are regularly fringed by coral-reefs. A portion of the S.E.
part of _Curieuse Island_, the N., and part of the S.W. shore of
_Praslin Island_, and the whole west side of _Digue Island_, appear
fringed. From a MS. account of these islands by Captain F. Moresby, in
the Admiralty, it appears that _Silhouette_ is also fringed; he states
that all these islands are formed of granite and quartz, that they rise
abruptly from the sea, and that “coral-reefs have grown round them, and
project for some distance.” Dr. Allan, of Forres, who visited these
islands, informs me that there is no deep water between the reefs and
the shore. The above specified points have been coloured red.
_Amirantes Islands:_ The small islands of this neighbouring group,
according to the MS. account of them by Captain F. Moresby, are
situated on an extensive bank; they consist of the debris of corals and
shells; are only about twenty feet in height, and are environed by
reefs, some attached to the shore, and some rather distant from it.—I
have taken great pains to procure plans and information regarding the
several islands lying between S.E. and S.W. of the Amirantes, and the
Seychelles; relying chiefly on Captain F. Moresby and Dr. Allan, it
appears that the greater number, namely—_Platte_, _Alphonse_,
_Coetivi_, _Galega_, _Providence_, _St. Pierre_, _Astova_,
_Assomption_, and _Glorioso_, are low, formed of sand or coral-rock,
and irregularly shaped; they are situated on very extensive banks, and
are connected with great coral-reefs. Galega is said by Dr. Allan, to
be rather higher than the other islands; and St. Pierre is described by
Captain F. Moresby, as being cavernous throughout, and as not
consisting of either limestone or granite. These islands, as well as
the Amirantes, certainly are not atoll-formed, and they differ as a
group from every other group with which I am acquainted; I have not
coloured them; but probably the reefs belong to the fringing class.
Their formation is attributed, both by Dr. Allan and Captain F.
Moresby, to the action of the currents, here exceedingly violent, on
banks, which no doubt have had an independent geological origin. They
resemble in many respects some islands and banks in the West Indies,
which owe their origin to a similar agency, in conjunction with an
elevation of the entire area. In close vicinity to the several islands,
there are three others of an apparently different nature: first, _Juan
de Nova_, which appears from some plans and accounts to be an atoll;
but from others does not appear to be so; not coloured. Secondly
_Cosmoledo;_ “this group consists of a ring of coral, ten leagues in
circumference, and a quarter of a mile broad in some places, enclosing
a magnificent lagoon, into which there did not appear a single opening”
(Horsburgh, volume i., page 151); coloured blue. Thirdly, _Aldabra;_ it
consists of three islets, about twenty-five feet in height, with red
cliffs (Horsburgh, volume i., page 176) surrounding a very shallow
basin or lagoon. The sea is profoundly deep close to the shore. Viewing
this island in a chart, it would be thought an atoll; but the foregoing
description shows that there is something different in its nature; Dr.
Allan also states that it is cavernous, and that the coral-rock has a
vitrified appearance. Is it an upheaved atoll, or the crater of a
volcano?—uncoloured.
COMORO GROUP.—_Mayotta_, according to Horsburgh (volume i., page 216,
4th edition), is completely surrounded by a reef, which runs at the
distance of three, four, and in some places even five miles from the
land; in an old chart, published by Dalrymple, a depth in many places
of thirty-six and thirty-eight fathoms is laid down within the reef. In
the same chart, the space of open water within the reef in some parts
is even more than three miles wide: the land is bold and peaked; this
island, therefore, is encircled by a well-characterised barrier-reef,
and is coloured pale blue.—_Johanna;_ Horsburgh says (volume I. page
217) this island from the N.W. to the S.W. point, is bounded by a reef,
at the distance of two miles from the shore; in some parts, however,
the reef must be attached, since Lieutenant Boteler (“Narr.” volume i.,
page 161) describes a passage through it, within which there is room
only for a few boats. Its height, as I am informed by Dr. Allan, is
about 3,500 feet; it is very precipitous, and is composed of granite,
greenstone, and quartz; coloured blue.—_Mohilla;_ on the S. side of
this island there is anchorage, in from thirty to forty-five fathoms,
between a reef and the shore (Horsburgh, volume i., page 214); in
Captain Owen’s chart of Madagascar, this island is represented as
encircled; coloured blue.—_Great Comoro Island_ is, as I am informed by
Dr. Allan, about 8,000 feet high, and apparently volcanic; it is not
regularly encircled; but reefs of various shapes and dimensions, jut
out from every headland on the W., S., and S.E. coasts, inside of which
reefs there are channels, often parallel with the shore, with deep
water. On the north-western coasts the reefs appear attached to the
shores. The land near the coast is in some places bold, but generally
speaking it is flat; Horsburgh says (volume i., page 214) the water is
profoundly deep close to the _shore_, from which expression I presume
some parts are without reefs. From this description I apprehend the
reef belongs to the barrier class; but I have not coloured it, as most
of the charts which I have seen, represent the reefs round it as very
much less extensive than round the other islands in the group.